(* Title : Lim.ML
Author : Jacques D. Fleuriot
Copyright : 1998 University of Cambridge
Description : Theory of limits, continuity and
differentiation of real=>real functions
*)
fun ARITH_PROVE str = prove_goal thy str
(fn prems => [cut_facts_tac prems 1,arith_tac 1]);
Goal "(x + - a = (#0::real)) = (x=a)";
by (arith_tac 1);
qed "real_add_minus_iff";
Addsimps [real_add_minus_iff];
(*---------------------------------------------------------------
Theory of limits, continuity and differentiation of
real=>real functions
----------------------------------------------------------------*)
Goalw [LIM_def] "(f -- a --> L) = (ALL r. #0 < r --> \
\ (EX s. #0 < s & (ALL x. (x ~= a & (abs(x + -a) < s) \
\ --> abs(f x + -L) < r))))";
by Auto_tac;
qed "LIM_iff";
Goalw [LIM_def]
"!!a. [| f -- a --> L; #0 < r |] \
\ ==> (EX s. #0 < s & (ALL x. (x ~= a \
\ & (abs(x + -a) < s) --> abs(f x + -L) < r)))";
by Auto_tac;
qed "LIMD";
Goalw [LIM_def] "(%x. k) -- x --> k";
by Auto_tac;
qed "LIM_const";
Addsimps [LIM_const];
(***-----------------------------------------------------------***)
(*** Some Purely Standard Proofs - Can be used for comparison ***)
(***-----------------------------------------------------------***)
(*---------------
LIM_add
---------------*)
Goalw [LIM_def]
"[| f -- x --> l; g -- x --> m |] \
\ ==> (%x. f(x) + g(x)) -- x --> (l + m)";
by (Step_tac 1);
by (REPEAT(dres_inst_tac [("x","r*inverse(#1 + #1)")] spec 1));
by (dtac (rename_numerals (real_zero_less_two RS real_inverse_gt_zero
RSN (2,real_mult_less_mono2))) 1);
by (Asm_full_simp_tac 1);
by (Clarify_tac 1);
by (res_inst_tac [("R1.0","s"),("R2.0","sa")]
real_linear_less2 1);
by (res_inst_tac [("x","s")] exI 1);
by (res_inst_tac [("x","sa")] exI 2);
by (res_inst_tac [("x","sa")] exI 3);
by (Step_tac 1);
by (REPEAT(dres_inst_tac [("x","xa")] spec 1)
THEN step_tac (claset() addSEs [real_less_trans]) 1);
by (REPEAT(dres_inst_tac [("x","xa")] spec 2)
THEN step_tac (claset() addSEs [real_less_trans]) 2);
by (REPEAT(dres_inst_tac [("x","xa")] spec 3)
THEN step_tac (claset() addSEs [real_less_trans]) 3);
by (ALLGOALS(rtac (abs_sum_triangle_ineq RS real_le_less_trans)));
by (ALLGOALS(rtac (real_sum_of_halves RS subst)));
by (auto_tac (claset() addIs [real_add_less_mono],simpset()));
qed "LIM_add";
Goalw [LIM_def] "f -- a --> L ==> (%x. -f(x)) -- a --> -L";
by (full_simp_tac (simpset() addsimps [real_minus_add_distrib RS sym,
abs_minus_cancel]
delsimps [real_minus_add_distrib,real_minus_minus]) 1);
qed "LIM_minus";
(*----------------------------------------------
LIM_add_minus
----------------------------------------------*)
Goal "[| f -- x --> l; g -- x --> m |] \
\ ==> (%x. f(x) + -g(x)) -- x --> (l + -m)";
by (blast_tac (claset() addDs [LIM_add,LIM_minus]) 1);
qed "LIM_add_minus";
(*----------------------------------------------
LIM_zero
----------------------------------------------*)
Goal "f -- a --> l ==> (%x. f(x) + -l) -- a --> #0";
by (res_inst_tac [("z1","l")] (rename_numerals (real_add_minus RS subst)) 1);
by (rtac LIM_add_minus 1 THEN Auto_tac);
qed "LIM_zero";
(*--------------------------
Limit not zero
--------------------------*)
Goalw [LIM_def] "k ~= #0 ==> ~ ((%x. k) -- x --> #0)";
by (res_inst_tac [("R1.0","k"),("R2.0","#0")] real_linear_less2 1);
by (auto_tac (claset(),simpset() addsimps [abs_minus_eqI2,abs_eqI2]));
by (dtac (rename_numerals (real_minus_zero_less_iff RS iffD2)) 1);
by (res_inst_tac [("x","-k")] exI 1);
by (res_inst_tac [("x","k")] exI 2);
by Auto_tac;
by (ALLGOALS(dres_inst_tac [("y","s")] real_dense));
by (Step_tac 1);
by (ALLGOALS(res_inst_tac [("x","r + x")] exI));
by (auto_tac (claset(),simpset() addsimps [real_add_assoc,abs_eqI2]));
qed "LIM_not_zero";
(* [| k ~= #0; (%x. k) -- x --> #0 |] ==> R *)
bind_thm("LIM_not_zeroE", (LIM_not_zero RS notE));
Goal "(%x. k) -- x --> L ==> k = L";
by (rtac ccontr 1);
by (dtac LIM_zero 1);
by (rtac LIM_not_zeroE 1 THEN assume_tac 2);
by (arith_tac 1);
qed "LIM_const_eq";
(*------------------------
Limit is Unique
------------------------*)
Goal "[| f -- x --> L; f -- x --> M |] ==> L = M";
by (dtac LIM_minus 1);
by (dtac LIM_add 1 THEN assume_tac 1);
by (auto_tac (claset() addSDs [LIM_const_eq RS sym],
simpset()));
qed "LIM_unique";
(*-------------
LIM_mult_zero
-------------*)
Goalw [LIM_def] "!!f. [| f -- x --> #0; g -- x --> #0 |] \
\ ==> (%x. f(x)*g(x)) -- x --> #0";
by (Step_tac 1);
by (dres_inst_tac [("x","#1")] spec 1);
by (dres_inst_tac [("x","r")] spec 1);
by (cut_facts_tac [real_zero_less_one] 1);
by (asm_full_simp_tac (simpset() addsimps
[abs_mult]) 1);
by (Clarify_tac 1);
by (res_inst_tac [("R1.0","s"),("R2.0","sa")]
real_linear_less2 1);
by (res_inst_tac [("x","s")] exI 1);
by (res_inst_tac [("x","sa")] exI 2);
by (res_inst_tac [("x","sa")] exI 3);
by (Step_tac 1);
by (REPEAT(dres_inst_tac [("x","xa")] spec 1)
THEN step_tac (claset() addSEs [real_less_trans]) 1);
by (REPEAT(dres_inst_tac [("x","xa")] spec 2)
THEN step_tac (claset() addSEs [real_less_trans]) 2);
by (REPEAT(dres_inst_tac [("x","xa")] spec 3)
THEN step_tac (claset() addSEs [real_less_trans]) 3);
by (ALLGOALS(res_inst_tac [("t","r")] (real_mult_1 RS subst)));
by (ALLGOALS(rtac abs_mult_less2));
by Auto_tac;
qed "LIM_mult_zero";
Goalw [LIM_def] "(%x. x) -- a --> a";
by (Auto_tac);
qed "LIM_self";
(*--------------------------------------------------------------
Limits are equal for functions equal except at limit point
--------------------------------------------------------------*)
Goalw [LIM_def]
"[| ALL x. x ~= a --> (f x = g x) |] \
\ ==> (f -- a --> l) = (g -- a --> l)";
by (auto_tac (claset(), simpset() addsimps [real_add_minus_iff]));
qed "LIM_equal";
Goal "[| (%x. f(x) + -g(x)) -- a --> #0; \
\ g -- a --> l |] \
\ ==> f -- a --> l";
by (dtac LIM_add 1 THEN assume_tac 1);
by (auto_tac (claset(), simpset() addsimps [real_add_assoc]));
qed "LIM_trans";
(***-------------------------------------------------------------***)
(*** End of Purely Standard Proofs ***)
(***-------------------------------------------------------------***)
(*--------------------------------------------------------------
Standard and NS definitions of Limit
--------------------------------------------------------------*)
Goalw [LIM_def,NSLIM_def,inf_close_def]
"f -- x --> L ==> f -- x --NS> L";
by (asm_full_simp_tac
(simpset() addsimps [Infinitesimal_FreeUltrafilterNat_iff]) 1);
by (Step_tac 1);
by (res_inst_tac [("z","xa")] eq_Abs_hypreal 1);
by (auto_tac (claset(),
simpset() addsimps [real_add_minus_iff,
starfun, hypreal_minus,hypreal_of_real_minus RS sym,
hypreal_of_real_def, hypreal_add]));
by (rtac bexI 1 THEN rtac lemma_hyprel_refl 2 THEN Step_tac 1);
by (dres_inst_tac [("x","u")] spec 1 THEN Clarify_tac 1);
by (dres_inst_tac [("x","s")] spec 1 THEN Clarify_tac 1);
by (subgoal_tac "ALL n::nat. (xa n) ~= x & \
\ abs ((xa n) + - x) < s --> abs (f (xa n) + - L) < u" 1);
by (Blast_tac 2);
by (dtac FreeUltrafilterNat_all 1);
by (Ultra_tac 1);
qed "LIM_NSLIM";
(*---------------------------------------------------------------------
Limit: NS definition ==> standard definition
---------------------------------------------------------------------*)
Goal "ALL s. #0 < s --> (EX xa. xa ~= x & \
\ abs (xa + - x) < s & r <= abs (f xa + -L)) \
\ ==> ALL n::nat. EX xa. xa ~= x & \
\ abs(xa + -x) < inverse(real_of_posnat n) & r <= abs(f xa + -L)";
by (Step_tac 1);
by (cut_inst_tac [("n1","n")] (real_of_posnat_gt_zero RS real_inverse_gt_zero) 1);
by Auto_tac;
val lemma_LIM = result();
Goal "ALL s. #0 < s --> (EX xa. xa ~= x & \
\ abs (xa + - x) < s & r <= abs (f xa + -L)) \
\ ==> EX X. ALL n::nat. X n ~= x & \
\ abs(X n + -x) < inverse(real_of_posnat n) & r <= abs(f (X n) + -L)";
by (dtac lemma_LIM 1);
by (dtac choice 1);
by (Blast_tac 1);
val lemma_skolemize_LIM2 = result();
Goal "!!X. ALL n. X n ~= x & \
\ abs (X n + - x) < inverse (real_of_posnat n) & \
\ r <= abs (f (X n) + - L) ==> \
\ ALL n. abs (X n + - x) < inverse (real_of_posnat n)";
by (Auto_tac );
val lemma_simp = result();
(*-------------------
NSLIM => LIM
-------------------*)
Goalw [LIM_def,NSLIM_def,inf_close_def]
"!!f. f -- x --NS> L ==> f -- x --> L";
by (asm_full_simp_tac
(simpset() addsimps [Infinitesimal_FreeUltrafilterNat_iff]) 1);
by (EVERY1[Step_tac, rtac ccontr, Asm_full_simp_tac]);
by (fold_tac [real_le_def]);
by (dtac lemma_skolemize_LIM2 1);
by (Step_tac 1);
by (dres_inst_tac [("x","Abs_hypreal(hyprel^^{X})")] spec 1);
by (asm_full_simp_tac
(simpset() addsimps [starfun,
hypreal_minus,hypreal_of_real_minus RS sym,
hypreal_of_real_def,hypreal_add]) 1);
by (Step_tac 1);
by (dtac (lemma_simp RS real_seq_to_hypreal_Infinitesimal) 1);
by (asm_full_simp_tac
(simpset() addsimps
[Infinitesimal_FreeUltrafilterNat_iff,hypreal_of_real_def,
hypreal_minus,hypreal_of_real_minus,hypreal_add]) 1);
by (Blast_tac 1);
by (rotate_tac 2 1);
by (dres_inst_tac [("x","r")] spec 1);
by (Clarify_tac 1);
by (dtac FreeUltrafilterNat_all 1);
by (Ultra_tac 1);
qed "NSLIM_LIM";
(**** Key result ****)
Goal "(f -- x --> L) = (f -- x --NS> L)";
by (blast_tac (claset() addIs [LIM_NSLIM,NSLIM_LIM]) 1);
qed "LIM_NSLIM_iff";
(*-------------------------------------------------------------------*)
(* Proving properties of limits using nonstandard definition and *)
(* hence, the properties hold for standard limits as well *)
(*-------------------------------------------------------------------*)
(*------------------------------------------------
NSLIM_mult and hence (trivially) LIM_mult
------------------------------------------------*)
Goalw [NSLIM_def]
"[| f -- x --NS> l; g -- x --NS> m |] \
\ ==> (%x. f(x) * g(x)) -- x --NS> (l * m)";
by (auto_tac (claset() addSIs [starfun_mult_HFinite_inf_close],
simpset() addsimps [hypreal_of_real_mult]));
qed "NSLIM_mult";
Goal "[| f -- x --> l; g -- x --> m |] \
\ ==> (%x. f(x) * g(x)) -- x --> (l * m)";
by (asm_full_simp_tac (simpset() addsimps [LIM_NSLIM_iff,
NSLIM_mult]) 1);
qed "LIM_mult2";
(*----------------------------------------------
NSLIM_add and hence (trivially) LIM_add
Note the much shorter proof
----------------------------------------------*)
Goalw [NSLIM_def]
"[| f -- x --NS> l; g -- x --NS> m |] \
\ ==> (%x. f(x) + g(x)) -- x --NS> (l + m)";
by (auto_tac (claset() addSIs [starfun_add_inf_close],
simpset() addsimps [hypreal_of_real_add]));
qed "NSLIM_add";
Goal "[| f -- x --> l; g -- x --> m |] \
\ ==> (%x. f(x) + g(x)) -- x --> (l + m)";
by (asm_full_simp_tac (simpset() addsimps [LIM_NSLIM_iff,
NSLIM_add]) 1);
qed "LIM_add2";
(*----------------------------------------------
NSLIM_const
----------------------------------------------*)
Goalw [NSLIM_def] "(%x. k) -- x --NS> k";
by (Auto_tac);
qed "NSLIM_const";
Addsimps [NSLIM_const];
Goal "(%x. k) -- x --> k";
by (asm_full_simp_tac (simpset() addsimps [LIM_NSLIM_iff]) 1);
qed "LIM_const2";
(*----------------------------------------------
NSLIM_minus
----------------------------------------------*)
Goalw [NSLIM_def]
"f -- a --NS> L ==> (%x. -f(x)) -- a --NS> -L";
by (auto_tac (claset() addIs [inf_close_minus],
simpset() addsimps [starfun_minus RS sym,
hypreal_of_real_minus]));
qed "NSLIM_minus";
Goal "f -- a --> L ==> (%x. -f(x)) -- a --> -L";
by (asm_full_simp_tac (simpset() addsimps [LIM_NSLIM_iff,
NSLIM_minus]) 1);
qed "LIM_minus2";
(*----------------------------------------------
NSLIM_add_minus
----------------------------------------------*)
Goal "!!f. [| f -- x --NS> l; g -- x --NS> m |] \
\ ==> (%x. f(x) + -g(x)) -- x --NS> (l + -m)";
by (blast_tac (claset() addDs [NSLIM_add,NSLIM_minus]) 1);
qed "NSLIM_add_minus";
Goal "!!f. [| f -- x --> l; g -- x --> m |] \
\ ==> (%x. f(x) + -g(x)) -- x --> (l + -m)";
by (asm_full_simp_tac (simpset() addsimps [LIM_NSLIM_iff,
NSLIM_add_minus]) 1);
qed "LIM_add_minus2";
(*-----------------------------
NSLIM_inverse
-----------------------------*)
Goalw [NSLIM_def]
"!!f. [| f -- a --NS> L; \
\ L ~= #0 \
\ |] ==> (%x. inverse(f(x))) -- a --NS> (inverse L)";
by (Step_tac 1);
by (dtac spec 1 THEN auto_tac (claset(),simpset()
addsimps [hypreal_of_real_not_zero_iff RS sym,
hypreal_of_real_inverse RS sym]));
by (forward_tac [inf_close_hypreal_of_real_not_zero] 1
THEN assume_tac 1);
by (auto_tac (claset() addSEs [(starfun_inverse2 RS subst),
inf_close_inverse,hypreal_of_real_HFinite_diff_Infinitesimal],
simpset()));
qed "NSLIM_inverse";
Goal "[| f -- a --> L; \
\ L ~= #0 |] ==> (%x. inverse(f(x))) -- a --> (inverse L)";
by (asm_full_simp_tac (simpset() addsimps [LIM_NSLIM_iff,
NSLIM_inverse]) 1);
qed "LIM_inverse";
(*------------------------------
NSLIM_zero
------------------------------*)
Goal "f -- a --NS> l ==> (%x. f(x) + -l) -- a --NS> #0";
by (res_inst_tac [("z1","l")] (rename_numerals
(real_add_minus RS subst)) 1);
by (rtac NSLIM_add_minus 1 THEN Auto_tac);
qed "NSLIM_zero";
Goal "f -- a --> l ==> (%x. f(x) + -l) -- a --> #0";
by (asm_full_simp_tac (simpset() addsimps [LIM_NSLIM_iff,
NSLIM_zero]) 1);
qed "LIM_zero2";
Goal "(%x. f(x) - l) -- x --NS> #0 ==> f -- x --NS> l";
by (dres_inst_tac [("g","%x. l"),("m","l")] NSLIM_add 1);
by (auto_tac (claset(),simpset() addsimps [real_diff_def,
real_add_assoc]));
qed "NSLIM_zero_cancel";
Goal "(%x. f(x) - l) -- x --> #0 ==> f -- x --> l";
by (dres_inst_tac [("g","%x. l"),("m","l")] LIM_add 1);
by (auto_tac (claset(),simpset() addsimps [real_diff_def,
real_add_assoc]));
qed "LIM_zero_cancel";
(*--------------------------
NSLIM_not_zero
--------------------------*)
Goalw [NSLIM_def] "k ~= #0 ==> ~ ((%x. k) -- x --NS> #0)";
by (Auto_tac);
by (res_inst_tac [("x","hypreal_of_real x + ehr")] exI 1);
by (auto_tac (claset() addIs [Infinitesimal_add_inf_close_self
RS inf_close_sym],simpset()));
by (dres_inst_tac [("x1","-hypreal_of_real x")] (hypreal_add_left_cancel RS iffD2) 1);
by (asm_full_simp_tac (simpset() addsimps [hypreal_add_assoc RS sym,
hypreal_epsilon_not_zero]) 1);
qed "NSLIM_not_zero";
(* [| k ~= #0; (%x. k) -- x --NS> #0 |] ==> R *)
bind_thm("NSLIM_not_zeroE", (NSLIM_not_zero RS notE));
Goal "k ~= #0 ==> ~ ((%x. k) -- x --> #0)";
by (asm_full_simp_tac (simpset() addsimps [LIM_NSLIM_iff,
NSLIM_not_zero]) 1);
qed "LIM_not_zero2";
(*-------------------------------------
NSLIM of constant function
-------------------------------------*)
Goal "(%x. k) -- x --NS> L ==> k = L";
by (rtac ccontr 1);
by (dtac NSLIM_zero 1);
by (rtac NSLIM_not_zeroE 1 THEN assume_tac 2);
by (arith_tac 1);
qed "NSLIM_const_eq";
Goal "(%x. k) -- x --> L ==> k = L";
by (asm_full_simp_tac (simpset() addsimps [LIM_NSLIM_iff,
NSLIM_const_eq]) 1);
qed "LIM_const_eq2";
(*------------------------
NS Limit is Unique
------------------------*)
(* can actually be proved more easily by unfolding def! *)
Goal "[| f -- x --NS> L; f -- x --NS> M |] ==> L = M";
by (dtac NSLIM_minus 1);
by (dtac NSLIM_add 1 THEN assume_tac 1);
by (auto_tac (claset() addSDs [NSLIM_const_eq RS sym],
simpset() addsimps [real_add_minus]));
qed "NSLIM_unique";
Goal "[| f -- x --> L; f -- x --> M |] ==> L = M";
by (asm_full_simp_tac (simpset() addsimps [LIM_NSLIM_iff,
NSLIM_unique]) 1);
qed "LIM_unique2";
(*--------------------
NSLIM_mult_zero
--------------------*)
Goal "[| f -- x --NS> #0; g -- x --NS> #0 |] \
\ ==> (%x. f(x)*g(x)) -- x --NS> #0";
by (dtac NSLIM_mult 1 THEN Auto_tac);
qed "NSLIM_mult_zero";
(* we can use the corresponding thm LIM_mult2 *)
(* for standard definition of limit *)
Goal "[| f -- x --> #0; g -- x --> #0 |] \
\ ==> (%x. f(x)*g(x)) -- x --> #0";
by (dtac LIM_mult2 1 THEN Auto_tac);
qed "LIM_mult_zero2";
(*----------------------------
NSLIM_self
----------------------------*)
Goalw [NSLIM_def] "(%x. x) -- a --NS> a";
by (auto_tac (claset() addIs [starfun_Idfun_inf_close],simpset()));
qed "NSLIM_self";
Goal "(%x. x) -- a --> a";
by (simp_tac (simpset() addsimps [LIM_NSLIM_iff,NSLIM_self]) 1);
qed "LIM_self2";
(*-----------------------------------------------------------------------------
Derivatives and Continuity - NS and Standard properties
-----------------------------------------------------------------------------*)
(*---------------
Continuity
---------------*)
Goalw [isNSCont_def]
"!!f. [| isNSCont f a; y @= hypreal_of_real a |] \
\ ==> (*f* f) y @= hypreal_of_real (f a)";
by (Blast_tac 1);
qed "isNSContD";
Goalw [isNSCont_def,NSLIM_def]
"!!f. isNSCont f a ==> f -- a --NS> (f a) ";
by (Blast_tac 1);
qed "isNSCont_NSLIM";
Goalw [isNSCont_def,NSLIM_def]
"!!f. f -- a --NS> (f a) ==> isNSCont f a";
by (Auto_tac);
by (res_inst_tac [("Q","y = hypreal_of_real a")]
(excluded_middle RS disjE) 1);
by (Auto_tac);
qed "NSLIM_isNSCont";
(*-----------------------------------------------------
NS continuity can be defined using NS Limit in
similar fashion to standard def of continuity
-----------------------------------------------------*)
Goal "(isNSCont f a) = (f -- a --NS> (f a))";
by (blast_tac (claset() addIs [isNSCont_NSLIM,NSLIM_isNSCont]) 1);
qed "isNSCont_NSLIM_iff";
(*----------------------------------------------
Hence, NS continuity can be given
in terms of standard limit
---------------------------------------------*)
Goal "(isNSCont f a) = (f -- a --> (f a))";
by (asm_full_simp_tac (simpset() addsimps
[LIM_NSLIM_iff,isNSCont_NSLIM_iff]) 1);
qed "isNSCont_LIM_iff";
(*-----------------------------------------------
Moreover, it's trivial now that NS continuity
is equivalent to standard continuity
-----------------------------------------------*)
Goalw [isCont_def] "(isNSCont f a) = (isCont f a)";
by (rtac isNSCont_LIM_iff 1);
qed "isNSCont_isCont_iff";
(*----------------------------------------
Standard continuity ==> NS continuity
----------------------------------------*)
Goal "!!f. isCont f a ==> isNSCont f a";
by (etac (isNSCont_isCont_iff RS iffD2) 1);
qed "isCont_isNSCont";
(*----------------------------------------
NS continuity ==> Standard continuity
----------------------------------------*)
Goal "!!f. isNSCont f a ==> isCont f a";
by (etac (isNSCont_isCont_iff RS iffD1) 1);
qed "isNSCont_isCont";
(*--------------------------------------------------------------------------
Alternative definition of continuity
--------------------------------------------------------------------------*)
(* Prove equivalence between NS limits - *)
(* seems easier than using standard def *)
Goalw [NSLIM_def]
"(f -- a --NS> L) = ((%h. f(a + h)) -- #0 --NS> L)";
by (auto_tac (claset(),simpset() addsimps [hypreal_of_real_zero]));
by (dres_inst_tac [("x","hypreal_of_real a + x")] spec 1);
by (dres_inst_tac [("x","-hypreal_of_real a + x")] spec 2);
by (Step_tac 1);
by (dtac (sym RS (hypreal_eq_minus_iff4 RS iffD1)) 1);
by (rtac ((mem_infmal_iff RS iffD2) RS
(Infinitesimal_add_inf_close_self RS inf_close_sym)) 2);
by (rtac (inf_close_minus_iff2 RS iffD1) 5);
by (asm_full_simp_tac (simpset() addsimps [hypreal_add_commute]) 4);
by (dtac (sym RS (hypreal_eq_minus_iff RS iffD2)) 4);
by (res_inst_tac [("z","x")] eq_Abs_hypreal 3);
by (res_inst_tac [("z","x")] eq_Abs_hypreal 6);
by (auto_tac (claset(),simpset() addsimps [starfun,
hypreal_of_real_def,hypreal_minus,hypreal_add,
real_add_assoc,inf_close_refl,hypreal_zero_def]));
qed "NSLIM_h_iff";
Goal "(f -- a --NS> f a) = ((%h. f(a + h)) -- #0 --NS> f a)";
by (rtac NSLIM_h_iff 1);
qed "NSLIM_isCont_iff";
Goal "(f -- a --> f a) = ((%h. f(a + h)) -- #0 --> f(a))";
by (asm_full_simp_tac (simpset() addsimps [LIM_NSLIM_iff,
NSLIM_isCont_iff]) 1);
qed "LIM_isCont_iff";
Goalw [isCont_def]
"(isCont f x) = ((%h. f(x + h)) -- #0 --> f(x))";
by (simp_tac (simpset() addsimps [LIM_isCont_iff]) 1);
qed "isCont_iff";
(*--------------------------------------------------------------------------
Immediate application of nonstandard criterion for continuity can offer
very simple proofs of some standard property of continuous functions
--------------------------------------------------------------------------*)
(*------------------------
sum continuous
------------------------*)
Goal "!!f. [| isCont f a; isCont g a |] ==> isCont (%x. f(x) + g(x)) a";
by (auto_tac (claset() addIs [starfun_add_inf_close],simpset() addsimps
[isNSCont_isCont_iff RS sym,isNSCont_def,hypreal_of_real_add]));
qed "isCont_add";
(*------------------------
mult continuous
------------------------*)
Goal "[| isCont f a; isCont g a |] ==> isCont (%x. f(x) * g(x)) a";
by (auto_tac (claset() addSIs [starfun_mult_HFinite_inf_close],simpset() addsimps
[isNSCont_isCont_iff RS sym,isNSCont_def,hypreal_of_real_mult]));
qed "isCont_mult";
(*-------------------------------------------
composition of continuous functions
Note very short straightforard proof!
------------------------------------------*)
Goal "[| isCont f a; isCont g (f a) |] \
\ ==> isCont (g o f) a";
by (auto_tac (claset(),simpset() addsimps [isNSCont_isCont_iff RS sym,
isNSCont_def,starfun_o RS sym]));
qed "isCont_o";
Goal "[| isCont f a; isCont g (f a) |] \
\ ==> isCont (%x. g (f x)) a";
by (auto_tac (claset() addDs [isCont_o],simpset() addsimps [o_def]));
qed "isCont_o2";
Goalw [isNSCont_def] "isNSCont f a ==> isNSCont (%x. - f x) a";
by (auto_tac (claset(),simpset() addsimps [starfun_minus RS sym,
hypreal_of_real_minus]));
qed "isNSCont_minus";
Goal "isCont f a ==> isCont (%x. - f x) a";
by (auto_tac (claset(),simpset() addsimps [isNSCont_isCont_iff RS sym,
isNSCont_minus]));
qed "isCont_minus";
Goalw [isCont_def]
"[| isCont f x; f x ~= #0 |] ==> isCont (%x. inverse (f x)) x";
by (blast_tac (claset() addIs [LIM_inverse]) 1);
qed "isCont_inverse";
Goal "[| isNSCont f x; f x ~= #0 |] ==> isNSCont (%x. inverse (f x)) x";
by (auto_tac (claset() addIs [isCont_inverse],simpset() addsimps
[isNSCont_isCont_iff]));
qed "isNSCont_inverse";
Goalw [real_diff_def]
"[| isCont f a; isCont g a |] ==> isCont (%x. f(x) - g(x)) a";
by (auto_tac (claset() addIs [isCont_add,isCont_minus],simpset()));
qed "isCont_diff";
Goalw [isCont_def] "isCont (%x. k) a";
by (Simp_tac 1);
qed "isCont_const";
Addsimps [isCont_const];
Goalw [isNSCont_def] "isNSCont (%x. k) a";
by (Simp_tac 1);
qed "isNSCont_const";
Addsimps [isNSCont_const];
Goalw [isNSCont_def] "isNSCont abs a";
by (auto_tac (claset() addIs [inf_close_hrabs],simpset() addsimps
[hypreal_of_real_hrabs RS sym,starfun_rabs_hrabs]));
qed "isNSCont_rabs";
Addsimps [isNSCont_rabs];
Goal "isCont abs a";
by (auto_tac (claset(),simpset() addsimps [isNSCont_isCont_iff RS sym]));
qed "isCont_rabs";
Addsimps [isCont_rabs];
(****************************************************************
(* Leave as commented until I add topology theory or remove? *)
(*------------------------------------------------------------
Elementary topology proof for a characterisation of
continuity now: a function f is continuous if and only
if the inverse image, {x. f(x) : A}, of any open set A
is always an open set
------------------------------------------------------------*)
Goal "!!A. [| isNSopen A; ALL x. isNSCont f x |] \
\ ==> isNSopen {x. f x : A}";
by (auto_tac (claset(),simpset() addsimps [isNSopen_iff1]));
by (dtac (mem_monad_inf_close RS inf_close_sym) 1);
by (dres_inst_tac [("x","a")] spec 1);
by (dtac isNSContD 1 THEN assume_tac 1);
by (dtac bspec 1 THEN assume_tac 1);
by (dres_inst_tac [("x","( *f* f) x")] inf_close_mem_monad2 1);
by (blast_tac (claset() addIs [starfun_mem_starset]) 1);
qed "isNSCont_isNSopen";
Goalw [isNSCont_def]
"!!x. ALL A. isNSopen A --> isNSopen {x. f x : A} \
\ ==> isNSCont f x";
by (auto_tac (claset() addSIs [(mem_infmal_iff RS iffD1) RS
(inf_close_minus_iff RS iffD2)],simpset() addsimps
[Infinitesimal_def,SReal_iff]));
by (dres_inst_tac [("x","{z. abs(z + -f(x)) < ya}")] spec 1);
by (etac (isNSopen_open_interval RSN (2,impE)) 1);
by (auto_tac (claset(),simpset() addsimps [isNSopen_def,isNSnbhd_def]));
by (dres_inst_tac [("x","x")] spec 1);
by (auto_tac (claset() addDs [inf_close_sym RS inf_close_mem_monad],
simpset() addsimps [hypreal_of_real_zero RS sym,STAR_starfun_rabs_add_minus]));
qed "isNSopen_isNSCont";
Goal "(ALL x. isNSCont f x) = \
\ (ALL A. isNSopen A --> isNSopen {x. f(x) : A})";
by (blast_tac (claset() addIs [isNSCont_isNSopen,
isNSopen_isNSCont]) 1);
qed "isNSCont_isNSopen_iff";
(*------- Standard version of same theorem --------*)
Goal "(ALL x. isCont f x) = \
\ (ALL A. isopen A --> isopen {x. f(x) : A})";
by (auto_tac (claset() addSIs [isNSCont_isNSopen_iff],
simpset() addsimps [isNSopen_isopen_iff RS sym,
isNSCont_isCont_iff RS sym]));
qed "isCont_isopen_iff";
*******************************************************************)
(*-----------------------------------------------------------------
Uniform continuity
------------------------------------------------------------------*)
Goalw [isNSUCont_def]
"[| isNSUCont f; x @= y|] ==> (*f* f) x @= (*f* f) y";
by (Blast_tac 1);
qed "isNSUContD";
Goalw [isUCont_def,isCont_def,LIM_def]
"isUCont f ==> EX x. isCont f x";
by (Force_tac 1);
qed "isUCont_isCont";
Goalw [isNSUCont_def,isUCont_def,inf_close_def]
"isUCont f ==> isNSUCont f";
by (asm_full_simp_tac (simpset() addsimps
[Infinitesimal_FreeUltrafilterNat_iff]) 1);
by (Step_tac 1);
by (res_inst_tac [("z","x")] eq_Abs_hypreal 1);
by (res_inst_tac [("z","y")] eq_Abs_hypreal 1);
by (auto_tac (claset(),simpset() addsimps [starfun,
hypreal_minus, hypreal_add]));
by (rtac bexI 1 THEN rtac lemma_hyprel_refl 2 THEN Step_tac 1);
by (dres_inst_tac [("x","u")] spec 1 THEN Clarify_tac 1);
by (dres_inst_tac [("x","s")] spec 1 THEN Clarify_tac 1);
by (subgoal_tac "ALL n::nat. abs ((xa n) + - (xb n)) < s --> abs (f (xa n) + - f (xb n)) < u" 1);
by (Blast_tac 2);
by (thin_tac "ALL x y. abs (x + - y) < s --> abs (f x + - f y) < u" 1);
by (dtac FreeUltrafilterNat_all 1);
by (Ultra_tac 1);
qed "isUCont_isNSUCont";
Goal "!!x. ALL s. #0 < s --> \
\ (EX xa y. abs (xa + - y) < s & \
\ r <= abs (f xa + -f y)) ==> \
\ ALL n::nat. EX xa y. \
\ abs(xa + -y) < inverse(real_of_posnat n) & \
\ r <= abs(f xa + -f y)";
by (Step_tac 1);
by (cut_inst_tac [("n1","n")] (real_of_posnat_gt_zero RS real_inverse_gt_zero) 1);
by Auto_tac;
val lemma_LIMu = result();
Goal "!!x. ALL s. #0 < s --> \
\ (EX xa y. abs (xa + - y) < s & \
\ r <= abs (f xa + -f y)) ==> \
\ EX X Y. ALL n::nat. \
\ abs(X n + -(Y n)) < inverse(real_of_posnat n) & \
\ r <= abs(f (X n) + -f (Y n))";
by (dtac lemma_LIMu 1);
by (dtac choice 1);
by (Step_tac 1);
by (dtac choice 1);
by (Blast_tac 1);
val lemma_skolemize_LIM2u = result();
Goal "ALL n. abs (X n + -Y n) < inverse (real_of_posnat n) & \
\ r <= abs (f (X n) + - f(Y n)) ==> \
\ ALL n. abs (X n + - Y n) < inverse (real_of_posnat n)";
by (Auto_tac );
val lemma_simpu = result();
Goal "{n. f (X n) + - f(Y n) = Ya n} Int \
\ {n. abs (X n + - Y n) < inverse (real_of_posnat n) & \
\ r <= abs (f (X n) + - f(Y n))} <= \
\ {n. r <= abs (Ya n)}";
by (Auto_tac);
val lemma_Intu = result ();
Goalw [isNSUCont_def,isUCont_def,inf_close_def]
"isNSUCont f ==> isUCont f";
by (asm_full_simp_tac (simpset() addsimps
[Infinitesimal_FreeUltrafilterNat_iff]) 1);
by (EVERY1[Step_tac, rtac ccontr, Asm_full_simp_tac]);
by (fold_tac [real_le_def]);
by (dtac lemma_skolemize_LIM2u 1);
by (Step_tac 1);
by (dres_inst_tac [("x","Abs_hypreal(hyprel^^{X})")] spec 1);
by (dres_inst_tac [("x","Abs_hypreal(hyprel^^{Y})")] spec 1);
by (asm_full_simp_tac (simpset() addsimps [starfun,
hypreal_minus,hypreal_add]) 1);
by (Auto_tac);
by (dtac (lemma_simpu RS real_seq_to_hypreal_Infinitesimal2) 1);
by (asm_full_simp_tac (simpset() addsimps
[Infinitesimal_FreeUltrafilterNat_iff,
hypreal_minus,hypreal_add]) 1);
by (Blast_tac 1);
by (rotate_tac 2 1);
by (dres_inst_tac [("x","r")] spec 1);
by (Clarify_tac 1);
by (dtac FreeUltrafilterNat_all 1);
by (Ultra_tac 1);
qed "isNSUCont_isUCont";
(*------------------------------------------------------------------
Derivatives
------------------------------------------------------------------*)
Goalw [deriv_def]
"(DERIV f x :> D) = ((%h. (f(x + h) + - f(x))*inverse(h)) -- #0 --> D)";
by (Blast_tac 1);
qed "DERIV_iff";
Goalw [deriv_def]
"(DERIV f x :> D) = ((%h. (f(x + h) + - f(x))*inverse(h)) -- #0 --NS> D)";
by (simp_tac (simpset() addsimps [LIM_NSLIM_iff]) 1);
qed "DERIV_NS_iff";
Goalw [deriv_def]
"DERIV f x :> D \
\ ==> (%h. (f(x + h) + - f(x))*inverse(h)) -- #0 --> D";
by (Blast_tac 1);
qed "DERIVD";
Goalw [deriv_def] "DERIV f x :> D ==> \
\ (%h. (f(x + h) + - f(x))*inverse(h)) -- #0 --NS> D";
by (asm_full_simp_tac (simpset() addsimps [LIM_NSLIM_iff]) 1);
qed "NS_DERIVD";
(* Uniqueness *)
Goalw [deriv_def]
"!!f. [| DERIV f x :> D; DERIV f x :> E |] ==> D = E";
by (blast_tac (claset() addIs [LIM_unique]) 1);
qed "DERIV_unique";
Goalw [nsderiv_def]
"!!f. [| NSDERIV f x :> D; NSDERIV f x :> E |] ==> D = E";
by (cut_facts_tac [Infinitesimal_epsilon,
hypreal_epsilon_not_zero] 1);
by (auto_tac (claset() addSDs [bspec] addSIs
[inj_hypreal_of_real RS injD] addDs [inf_close_trans3],simpset()));
qed "NSDeriv_unique";
(*------------------------------------------------------------------------
Differentiable
------------------------------------------------------------------------*)
Goalw [differentiable_def]
"!!f. f differentiable x ==> EX D. DERIV f x :> D";
by (assume_tac 1);
qed "differentiableD";
Goalw [differentiable_def]
"!!f. DERIV f x :> D ==> f differentiable x";
by (Blast_tac 1);
qed "differentiableI";
Goalw [NSdifferentiable_def]
"!!f. f NSdifferentiable x ==> EX D. NSDERIV f x :> D";
by (assume_tac 1);
qed "NSdifferentiableD";
Goalw [NSdifferentiable_def]
"!!f. NSDERIV f x :> D ==> f NSdifferentiable x";
by (Blast_tac 1);
qed "NSdifferentiableI";
(*--------------------------------------------------------
Alternative definition for differentiability
-------------------------------------------------------*)
Goalw [LIM_def]
"((%h. (f(a + h) + - f(a))*inverse(h)) -- #0 --> D) = \
\ ((%x. (f(x) + -f(a))*inverse(x + -a)) -- a --> D)";
by (Step_tac 1);
by (ALLGOALS(dtac spec));
by (Step_tac 1);
by (Blast_tac 1 THEN Blast_tac 2);
by (ALLGOALS(res_inst_tac [("x","s")] exI));
by (Step_tac 1);
by (dres_inst_tac [("x","x + -a")] spec 1);
by (dres_inst_tac [("x","x + a")] spec 2);
by (auto_tac (claset(),simpset() addsimps
real_add_ac));
qed "DERIV_LIM_iff";
Goalw [deriv_def] "(DERIV f x :> D) = \
\ ((%z. (f(z) + -f(x))*inverse(z + -x)) -- x --> D)";
by (simp_tac (simpset() addsimps [DERIV_LIM_iff]) 1);
qed "DERIV_iff2";
(*--------------------------------------------------------
Equivalence of NS and standard defs of differentiation
-------------------------------------------------------*)
(*-------------------------------------------
First NSDERIV in terms of NSLIM
-------------------------------------------*)
(*--- first equivalence ---*)
Goalw [nsderiv_def,NSLIM_def]
"(NSDERIV f x :> D) = ((%h. (f(x + h) + - f(x))*inverse(h)) -- #0 --NS> D)";
by (auto_tac (claset(),simpset() addsimps [hypreal_of_real_zero]));
by (dres_inst_tac [("x","xa")] bspec 1);
by (rtac ccontr 3);
by (dres_inst_tac [("x","h")] spec 3);
by (auto_tac (claset(),simpset() addsimps [mem_infmal_iff,
starfun_mult RS sym,starfun_inverse_inverse,starfun_add RS sym,
hypreal_of_real_minus,starfun_lambda_cancel]));
qed "NSDERIV_NSLIM_iff";
(*--- second equivalence ---*)
Goal "(NSDERIV f x :> D) = \
\ ((%z. (f(z) + -f(x))*inverse(z + -x)) -- x --NS> D)";
by (full_simp_tac (simpset() addsimps
[NSDERIV_NSLIM_iff,DERIV_LIM_iff,LIM_NSLIM_iff RS sym]) 1);
qed "NSDERIV_NSLIM_iff2";
(* while we're at it! *)
Goalw [real_diff_def]
"(NSDERIV f x :> D) = \
\ (ALL xa. \
\ xa ~= hypreal_of_real x & xa @= hypreal_of_real x --> \
\ (*f* (%z. (f z - f x) * inverse (z - x))) xa @= hypreal_of_real D)";
by (auto_tac (claset(),simpset() addsimps [NSDERIV_NSLIM_iff2,
NSLIM_def]));
qed "NSDERIV_iff2";
Addsimps [inf_close_refl];
Goal "(NSDERIV f x :> D) ==> \
\ (ALL xa. \
\ xa @= hypreal_of_real x --> \
\ (*f* (%z. f z - f x)) xa @= hypreal_of_real D * (xa - hypreal_of_real x))";
by (auto_tac (claset(),simpset() addsimps [NSDERIV_iff2]));
by (case_tac "xa = hypreal_of_real x" 1);
by (auto_tac (claset(),simpset() addsimps [hypreal_diff_def,
hypreal_of_real_zero]));
by (dres_inst_tac [("x","xa")] spec 1);
by Auto_tac;
by (dres_inst_tac [("c","xa - hypreal_of_real x"),("b","hypreal_of_real D")]
inf_close_mult1 1);
by (ALLGOALS(dtac (hypreal_not_eq_minus_iff RS iffD1)));
by (subgoal_tac "(*f* (%z. z - x)) xa ~= (0::hypreal)" 2);
by (dtac (starfun_inverse2 RS sym) 2);
by (auto_tac (claset() addDs [hypreal_mult_inverse_left],
simpset() addsimps [starfun_mult RS sym,
hypreal_mult_assoc,starfun_add RS sym,real_diff_def,
starfun_Id,hypreal_of_real_minus,hypreal_diff_def,
(inf_close_minus_iff RS iffD1) RS (mem_infmal_iff RS iffD2),
Infinitesimal_subset_HFinite RS subsetD]));
qed "NSDERIVD5";
Goal "(NSDERIV f x :> D) ==> \
\ (ALL h: Infinitesimal. \
\ ((*f* f)(hypreal_of_real x + h) - \
\ hypreal_of_real (f x))@= (hypreal_of_real D) * h)";
by (auto_tac (claset(),simpset() addsimps [nsderiv_def]));
by (case_tac "h = (0::hypreal)" 1);
by (auto_tac (claset(),simpset() addsimps [hypreal_diff_def]));
by (dres_inst_tac [("x","h")] bspec 1);
by (dres_inst_tac [("c","h")] inf_close_mult1 2);
by (auto_tac (claset() addIs [Infinitesimal_subset_HFinite RS subsetD],
simpset() addsimps [hypreal_mult_assoc,hypreal_diff_def]));
qed "NSDERIVD4";
Goal "(NSDERIV f x :> D) ==> \
\ (ALL h: Infinitesimal - {0}. \
\ ((*f* f)(hypreal_of_real x + h) - \
\ hypreal_of_real (f x))@= (hypreal_of_real D) * h)";
by (auto_tac (claset(),simpset() addsimps [nsderiv_def]));
by (rtac ccontr 1 THEN dres_inst_tac [("x","h")] bspec 1);
by (dres_inst_tac [("c","h")] inf_close_mult1 2);
by (auto_tac (claset() addIs [Infinitesimal_subset_HFinite RS subsetD],
simpset() addsimps [hypreal_mult_assoc,hypreal_diff_def]));
qed "NSDERIVD3";
(*--------------------------------------------------------------
Now equivalence between NSDERIV and DERIV
-------------------------------------------------------------*)
Goalw [deriv_def] "(NSDERIV f x :> D) = (DERIV f x :> D)";
by (simp_tac (simpset() addsimps [NSDERIV_NSLIM_iff,LIM_NSLIM_iff]) 1);
qed "NSDERIV_DERIV_iff";
(*---------------------------------------------------
Differentiability implies continuity
nice and simple "algebraic" proof
--------------------------------------------------*)
Goalw [nsderiv_def]
"NSDERIV f x :> D ==> isNSCont f x";
by (auto_tac (claset(),simpset() addsimps
[isNSCont_NSLIM_iff,NSLIM_def]));
by (dtac (inf_close_minus_iff RS iffD1) 1);
by (dtac (hypreal_not_eq_minus_iff RS iffD1) 1);
by (dres_inst_tac [("x","-hypreal_of_real x + xa")] bspec 1);
by (asm_full_simp_tac (simpset() addsimps
[hypreal_add_assoc RS sym]) 2);
by (auto_tac (claset(),simpset() addsimps
[mem_infmal_iff RS sym,hypreal_add_commute]));
by (dres_inst_tac [("c","xa + -hypreal_of_real x")] inf_close_mult1 1);
by (auto_tac (claset() addIs [Infinitesimal_subset_HFinite
RS subsetD],simpset() addsimps [hypreal_mult_assoc]));
by (dres_inst_tac [("x3","D")] (HFinite_hypreal_of_real RSN
(2,Infinitesimal_HFinite_mult) RS (mem_infmal_iff RS iffD1)) 1);
by (blast_tac (claset() addIs [inf_close_trans,
hypreal_mult_commute RS subst,
(inf_close_minus_iff RS iffD2)]) 1);
qed "NSDERIV_isNSCont";
(* Now Sandard proof *)
Goal "DERIV f x :> D ==> isCont f x";
by (asm_full_simp_tac (simpset() addsimps
[NSDERIV_DERIV_iff RS sym, isNSCont_isCont_iff RS sym,
NSDERIV_isNSCont]) 1);
qed "DERIV_isCont";
(*----------------------------------------------------------------------------
Differentiation rules for combinations of functions
follow from clear, straightforard, algebraic
manipulations
----------------------------------------------------------------------------*)
(*-------------------------
Constant function
------------------------*)
(* use simple constant nslimit theorem *)
Goal "(NSDERIV (%x. k) x :> #0)";
by (simp_tac (simpset() addsimps
[NSDERIV_NSLIM_iff,real_add_minus]) 1);
qed "NSDERIV_const";
Addsimps [NSDERIV_const];
Goal "(DERIV (%x. k) x :> #0)";
by (simp_tac (simpset() addsimps [NSDERIV_DERIV_iff RS sym]) 1);
qed "DERIV_const";
Addsimps [DERIV_const];
(*-----------------------------------------------------
Sum of functions- proved easily
----------------------------------------------------*)
Goal "[| NSDERIV f x :> Da; NSDERIV g x :> Db |] \
\ ==> NSDERIV (%x. f x + g x) x :> Da + Db";
by (asm_full_simp_tac (simpset() addsimps [NSDERIV_NSLIM_iff,
NSLIM_def]) 1 THEN REPEAT(Step_tac 1));
by (auto_tac (claset(),simpset() addsimps [starfun_add RS sym,
starfun_mult RS sym,hypreal_of_real_minus,hypreal_of_real_add,
hypreal_minus_add_distrib,hypreal_add_mult_distrib]));
by (thin_tac "xa @= hypreal_of_real #0" 1 THEN dtac inf_close_add 1);
by (auto_tac (claset(),simpset() addsimps hypreal_add_ac));
qed "NSDERIV_add";
(* Standard theorem *)
Goal "[| DERIV f x :> Da; DERIV g x :> Db |] \
\ ==> DERIV (%x. f x + g x) x :> Da + Db";
by (asm_full_simp_tac (simpset() addsimps [NSDERIV_add,
NSDERIV_DERIV_iff RS sym]) 1);
qed "DERIV_add";
(*-----------------------------------------------------
Product of functions - Proof is trivial but tedious
and long due to rearrangement of terms
----------------------------------------------------*)
(* lemma - terms manipulation tedious as usual*)
Goal "((a::real)*b) + -(c*d) = (b*(a + -c)) + \
\ (c*(b + -d))";
by (full_simp_tac (simpset() addsimps [real_add_mult_distrib2,
real_minus_mult_eq2 RS sym,real_mult_commute]) 1);
val lemma_nsderiv1 = result();
Goal "[| (x + y) * inverse z = hypreal_of_real D + yb; z ~= 0; \
\ z : Infinitesimal; yb : Infinitesimal |] \
\ ==> x + y @= 0";
by (forw_inst_tac [("c1","z")] (hypreal_mult_right_cancel
RS iffD2) 1 THEN assume_tac 1);
by (thin_tac "(x + y) * inverse z = hypreal_of_real D + yb" 1);
by (auto_tac (claset() addSIs [Infinitesimal_HFinite_mult2,
HFinite_add],simpset() addsimps [hypreal_mult_assoc,
mem_infmal_iff RS sym]));
by (etac (Infinitesimal_subset_HFinite RS subsetD) 1);
val lemma_nsderiv2 = result();
Goal "[| NSDERIV f x :> Da; NSDERIV g x :> Db |] \
\ ==> NSDERIV (%x. f x * g x) x :> (Da * g(x)) + (Db * f(x))";
by (asm_full_simp_tac (simpset() addsimps [NSDERIV_NSLIM_iff,
NSLIM_def]) 1 THEN REPEAT(Step_tac 1));
by (auto_tac (claset(),simpset() addsimps [starfun_mult RS sym,
starfun_add RS sym,starfun_lambda_cancel,
starfun_inverse_inverse,hypreal_of_real_zero,lemma_nsderiv1]));
by (simp_tac (simpset() addsimps [hypreal_add_mult_distrib]) 1);
by (REPEAT(dtac (bex_Infinitesimal_iff2 RS iffD2) 1));
by (auto_tac (claset(),simpset() addsimps [hypreal_mult_assoc,
hypreal_of_real_minus]));
by (dres_inst_tac [("D","Db")] lemma_nsderiv2 1);
by (dtac ((inf_close_minus_iff RS iffD2) RS
(bex_Infinitesimal_iff2 RS iffD2)) 4);
by (auto_tac (claset() addSIs [inf_close_add_mono1],
simpset() addsimps [hypreal_of_real_add,hypreal_add_mult_distrib,
hypreal_add_mult_distrib2,hypreal_of_real_mult,hypreal_mult_commute,
hypreal_add_assoc]));
by (res_inst_tac [("w1","hypreal_of_real Db * hypreal_of_real (f x)")]
(hypreal_add_commute RS subst) 1);
by (auto_tac (claset() addSIs [Infinitesimal_add_inf_close_self2 RS
inf_close_sym,Infinitesimal_add,Infinitesimal_mult,
Infinitesimal_hypreal_of_real_mult,Infinitesimal_hypreal_of_real_mult2 ],
simpset() addsimps [hypreal_add_assoc RS sym]));
qed "NSDERIV_mult";
Goal "[| DERIV f x :> Da; DERIV g x :> Db |] \
\ ==> DERIV (%x. f x * g x) x :> (Da * g(x)) + (Db * f(x))";
by (asm_full_simp_tac (simpset() addsimps [NSDERIV_mult,
NSDERIV_DERIV_iff RS sym]) 1);
qed "DERIV_mult";
(*----------------------------
Multiplying by a constant
---------------------------*)
Goal "NSDERIV f x :> D \
\ ==> NSDERIV (%x. c * f x) x :> c*D";
by (asm_full_simp_tac (simpset() addsimps [NSDERIV_NSLIM_iff,
real_minus_mult_eq2,real_add_mult_distrib2 RS sym,
real_mult_assoc] delsimps [real_minus_mult_eq2 RS sym]) 1);
by (etac (NSLIM_const RS NSLIM_mult) 1);
qed "NSDERIV_cmult";
(* let's do the standard proof though theorem *)
(* LIM_mult2 follows from a NS proof *)
Goalw [deriv_def]
"DERIV f x :> D \
\ ==> DERIV (%x. c * f x) x :> c*D";
by (asm_full_simp_tac (simpset() addsimps [
real_minus_mult_eq2,real_add_mult_distrib2 RS sym,
real_mult_assoc] delsimps [real_minus_mult_eq2 RS sym]) 1);
by (etac (LIM_const RS LIM_mult2) 1);
qed "DERIV_cmult";
(*--------------------------------
Negation of function
-------------------------------*)
Goal "NSDERIV f x :> D \
\ ==> NSDERIV (%x. -(f x)) x :> -D";
by (asm_full_simp_tac (simpset() addsimps [NSDERIV_NSLIM_iff]) 1);
by (res_inst_tac [("t","f x")] (real_minus_minus RS subst) 1);
by (asm_simp_tac (simpset() addsimps [real_minus_add_distrib RS sym,
real_minus_mult_eq1 RS sym] delsimps [real_minus_add_distrib,
real_minus_minus]) 1);
by (etac NSLIM_minus 1);
qed "NSDERIV_minus";
Goal "DERIV f x :> D \
\ ==> DERIV (%x. -(f x)) x :> -D";
by (asm_full_simp_tac (simpset() addsimps
[NSDERIV_minus,NSDERIV_DERIV_iff RS sym]) 1);
qed "DERIV_minus";
(*-------------------------------
Subtraction
------------------------------*)
Goal "[| NSDERIV f x :> Da; NSDERIV g x :> Db |] \
\ ==> NSDERIV (%x. f x + -g x) x :> Da + -Db";
by (blast_tac (claset() addDs [NSDERIV_add,NSDERIV_minus]) 1);
qed "NSDERIV_add_minus";
Goal "[| DERIV f x :> Da; DERIV g x :> Db |] \
\ ==> DERIV (%x. f x + -g x) x :> Da + -Db";
by (blast_tac (claset() addDs [DERIV_add,DERIV_minus]) 1);
qed "DERIV_add_minus";
Goalw [real_diff_def]
"[| NSDERIV f x :> Da; NSDERIV g x :> Db |] \
\ ==> NSDERIV (%x. f x - g x) x :> Da - Db";
by (blast_tac (claset() addIs [NSDERIV_add_minus]) 1);
qed "NSDERIV_diff";
Goalw [real_diff_def]
"[| DERIV f x :> Da; DERIV g x :> Db |] \
\ ==> DERIV (%x. f x - g x) x :> Da - Db";
by (blast_tac (claset() addIs [DERIV_add_minus]) 1);
qed "DERIV_diff";
(*---------------------------------------------------------------
(NS) Increment
---------------------------------------------------------------*)
Goalw [increment_def]
"f NSdifferentiable x ==> \
\ increment f x h = (*f* f) (hypreal_of_real(x) + h) + \
\ -hypreal_of_real (f x)";
by (Blast_tac 1);
qed "incrementI";
Goal "NSDERIV f x :> D ==> \
\ increment f x h = (*f* f) (hypreal_of_real(x) + h) + \
\ -hypreal_of_real (f x)";
by (etac (NSdifferentiableI RS incrementI) 1);
qed "incrementI2";
(* The Increment theorem -- Keisler p. 65 *)
Goal "[| NSDERIV f x :> D; h: Infinitesimal; h ~= 0 |] \
\ ==> EX e: Infinitesimal. increment f x h = hypreal_of_real(D)*h + e*h";
by (forw_inst_tac [("h","h")] incrementI2 1 THEN rewtac nsderiv_def);
by (dtac bspec 1 THEN Auto_tac);
by (dtac (bex_Infinitesimal_iff2 RS iffD2) 1 THEN Step_tac 1);
by (forw_inst_tac [("b1","hypreal_of_real(D) + y")]
(hypreal_mult_right_cancel RS iffD2) 1);
by (thin_tac "((*f* f) (hypreal_of_real(x) + h) + \
\ - hypreal_of_real (f x)) * inverse h = hypreal_of_real(D) + y" 2);
by (assume_tac 1);
by (auto_tac (claset(),simpset() addsimps [hypreal_mult_assoc,
hypreal_add_mult_distrib]));
qed "increment_thm";
Goal "[| NSDERIV f x :> D; h @= 0; h ~= 0 |] \
\ ==> EX e: Infinitesimal. increment f x h = \
\ hypreal_of_real(D)*h + e*h";
by (blast_tac (claset() addSDs [mem_infmal_iff RS iffD2]
addSIs [increment_thm]) 1);
qed "increment_thm2";
Goal "[| NSDERIV f x :> D; h @= 0; h ~= 0 |] \
\ ==> increment f x h @= 0";
by (dtac increment_thm2 1 THEN auto_tac (claset() addSIs
[Infinitesimal_HFinite_mult2,HFinite_add],simpset() addsimps
[hypreal_add_mult_distrib RS sym,mem_infmal_iff RS sym]));
by (etac (Infinitesimal_subset_HFinite RS subsetD) 1);
qed "increment_inf_close_zero";
(*---------------------------------------------------------------
Similarly to the above, the chain rule admits an entirely
straightforward derivation. Compare this with Harrison's
HOL proof of the chain rule, which proved to be trickier and
required an alternative characterisation of differentiability-
the so-called Carathedory derivative. Our main problem is
manipulation of terms.
--------------------------------------------------------------*)
(* lemmas *)
Goalw [nsderiv_def]
"!!f. [| NSDERIV g x :> D; \
\ (*f* g) (hypreal_of_real(x) + xa) = hypreal_of_real(g x);\
\ xa : Infinitesimal;\
\ xa ~= 0 \
\ |] ==> D = #0";
by (dtac bspec 1);
by (Auto_tac);
by (asm_full_simp_tac (simpset() addsimps
[hypreal_of_real_zero RS sym]) 1);
qed "NSDERIV_zero";
(* can be proved differently using NSLIM_isCont_iff *)
Goalw [nsderiv_def]
"!!f. [| NSDERIV f x :> D; \
\ h: Infinitesimal; h ~= 0 \
\ |] ==> (*f* f) (hypreal_of_real(x) + h) + -hypreal_of_real(f x) @= 0";
by (asm_full_simp_tac (simpset() addsimps
[mem_infmal_iff RS sym]) 1);
by (rtac Infinitesimal_ratio 1);
by (rtac inf_close_hypreal_of_real_HFinite 3);
by (Auto_tac);
qed "NSDERIV_inf_close";
(*---------------------------------------------------------------
from one version of differentiability
f(x) - f(a)
--------------- @= Db
x - a
---------------------------------------------------------------*)
Goal "[| NSDERIV f (g x) :> Da; \
\ (*f* g) (hypreal_of_real(x) + xa) ~= hypreal_of_real (g x); \
\ (*f* g) (hypreal_of_real(x) + xa) @= hypreal_of_real (g x) \
\ |] ==> ((*f* f) ((*f* g) (hypreal_of_real(x) + xa)) \
\ + - hypreal_of_real (f (g x)))* \
\ inverse ((*f* g) (hypreal_of_real(x) + xa) + \
\ - hypreal_of_real (g x)) @= hypreal_of_real(Da)";
by (auto_tac (claset(),simpset() addsimps [NSDERIV_NSLIM_iff2,
NSLIM_def,starfun_mult RS sym,hypreal_of_real_minus,
starfun_add RS sym,starfun_inverse3]));
qed "NSDERIVD1";
(*--------------------------------------------------------------
from other version of differentiability
f(x + h) - f(x)
----------------- @= Db
h
--------------------------------------------------------------*)
Goal "[| NSDERIV g x :> Db; xa: Infinitesimal; xa ~= 0 |] \
\ ==> ((*f* g) (hypreal_of_real(x) + xa) + - hypreal_of_real(g x)) * \
\ inverse xa @= hypreal_of_real(Db)";
by (auto_tac (claset(),simpset() addsimps [NSDERIV_NSLIM_iff,
NSLIM_def,starfun_mult RS sym,starfun_inverse_inverse,
starfun_add RS sym,hypreal_of_real_zero,mem_infmal_iff,
starfun_lambda_cancel,hypreal_of_real_minus]));
qed "NSDERIVD2";
(*---------------------------------------------
This proof uses both possible definitions
for differentiability.
--------------------------------------------*)
Goal "[| NSDERIV f (g x) :> Da; NSDERIV g x :> Db |] \
\ ==> NSDERIV (f o g) x :> Da * Db";
by (asm_simp_tac (simpset() addsimps [NSDERIV_NSLIM_iff,
NSLIM_def,hypreal_of_real_zero,mem_infmal_iff RS sym]) 1 THEN Step_tac 1);
by (forw_inst_tac [("f","g")] NSDERIV_inf_close 1);
by (auto_tac (claset(),simpset() addsimps [starfun_add RS sym,
hypreal_of_real_minus,starfun_inverse_inverse,hypreal_of_real_mult,
starfun_lambda_cancel2,starfun_o RS sym,starfun_mult RS sym]));
by (case_tac "(*f* g) (hypreal_of_real(x) + xa) = hypreal_of_real (g x)" 1);
by (dres_inst_tac [("g","g")] NSDERIV_zero 1);
by (auto_tac (claset(),simpset()
addsimps [hypreal_of_real_zero,inf_close_refl]));
by (res_inst_tac [("z1","(*f* g) (hypreal_of_real(x) + xa) + -hypreal_of_real (g x)"),
("y1","inverse xa")] (lemma_chain RS ssubst) 1);
by (etac (hypreal_not_eq_minus_iff RS iffD1) 1);
by (rtac inf_close_mult_hypreal_of_real 1);
by (blast_tac (claset() addIs [NSDERIVD1,
inf_close_minus_iff RS iffD2]) 1);
by (blast_tac (claset() addIs [NSDERIVD2]) 1);
qed "NSDERIV_chain";
(* standard version *)
Goal "!!f. [| DERIV f (g x) :> Da; \
\ DERIV g x :> Db \
\ |] ==> DERIV (f o g) x :> Da * Db";
by (asm_full_simp_tac (simpset() addsimps [NSDERIV_DERIV_iff RS sym,
NSDERIV_chain]) 1);
qed "DERIV_chain";
Goal "[| DERIV f (g x) :> Da; DERIV g x :> Db |] \
\ ==> DERIV (%x. f (g x)) x :> Da * Db";
by (auto_tac (claset() addDs [DERIV_chain], simpset() addsimps [o_def]));
qed "DERIV_chain2";
Goal "[| DERIV f x :> D; D = E |] ==> DERIV f x :> E";
by (Auto_tac);
val lemma_DERIV_tac = result();
(*------------------------------------------------------------------
Differentiation of natural number powers
------------------------------------------------------------------*)
Goal "NSDERIV (%x. x) x :> #1";
by (auto_tac (claset(),simpset() addsimps [NSDERIV_NSLIM_iff,
NSLIM_def,starfun_mult RS sym,starfun_Id,hypreal_of_real_zero,
starfun_inverse_inverse,hypreal_of_real_one]
@ real_add_ac));
qed "NSDERIV_Id";
Addsimps [NSDERIV_Id];
(*derivative of the identity function*)
Goal "DERIV (%x. x) x :> #1";
by (simp_tac (simpset() addsimps [NSDERIV_DERIV_iff RS sym]) 1);
qed "DERIV_Id";
Addsimps [DERIV_Id];
(*derivative of linear multiplication*)
Goal "DERIV (op * c) x :> c";
by (cut_inst_tac [("c","c"),("x","x")] (DERIV_Id RS DERIV_cmult) 1);
by (Asm_full_simp_tac 1);
qed "DERIV_cmult_Id";
Addsimps [DERIV_cmult_Id];
Goal "NSDERIV (op * c) x :> c";
by (simp_tac (simpset() addsimps [NSDERIV_DERIV_iff]) 1);
qed "NSDERIV_cmult_Id";
Addsimps [NSDERIV_cmult_Id];
Goal "DERIV (%x. x ^ n) x :> real_of_nat n * (x ^ (n - 1))";
by (induct_tac "n" 1);
by (dtac (DERIV_Id RS DERIV_mult) 2);
by (auto_tac (claset(),simpset() addsimps
[real_add_mult_distrib]));
by (case_tac "0 < n" 1);
by (dres_inst_tac [("x","x")] realpow_minus_mult 1);
by (auto_tac (claset(),simpset() addsimps
[real_mult_assoc,real_add_commute]));
qed "DERIV_pow";
(* NS version *)
Goal "NSDERIV (%x. x ^ n) x :> real_of_nat n * (x ^ (n - 1))";
by (simp_tac (simpset() addsimps [NSDERIV_DERIV_iff,DERIV_pow]) 1);
qed "NSDERIV_pow";
(*---------------------------------------------------------------
Power of -1
---------------------------------------------------------------*)
Goalw [nsderiv_def]
"x ~= #0 ==> NSDERIV (%x. inverse(x)) x :> (- (inverse x ^ 2))";
by (rtac ballI 1 THEN Asm_full_simp_tac 1 THEN Step_tac 1);
by (forward_tac [Infinitesimal_add_not_zero] 1);
by (auto_tac (claset(),simpset() addsimps [starfun_inverse_inverse,
hypreal_of_real_inverse RS sym,hypreal_of_real_minus,realpow_two,
hypreal_of_real_mult] delsimps [hypreal_minus_mult_eq1 RS
sym,hypreal_minus_mult_eq2 RS sym]));
by (dtac (hypreal_of_real_not_zero_iff RS iffD2) 1);
by (asm_full_simp_tac (simpset() addsimps [hypreal_inverse_add,
inverse_mult_eq RS sym, hypreal_minus_inverse RS sym]
@ hypreal_add_ac @ hypreal_mult_ac delsimps [hypreal_minus_mult_eq1 RS
sym,hypreal_minus_mult_eq2 RS sym] ) 1);
by (asm_simp_tac (simpset() addsimps [hypreal_mult_assoc RS sym,
hypreal_add_mult_distrib2] delsimps [hypreal_minus_mult_eq1 RS
sym,hypreal_minus_mult_eq2 RS sym]) 1);
by (dres_inst_tac [("x3","x") ] ((HFinite_hypreal_of_real RSN
(2,Infinitesimal_HFinite_mult2)) RS
(Infinitesimal_minus_iff RS iffD1)) 1);
by (forw_inst_tac [("x","hypreal_of_real x"),("y","hypreal_of_real x")] hypreal_mult_not_0 1);
by (res_inst_tac [("y"," inverse(- hypreal_of_real x * hypreal_of_real x)")] inf_close_trans 2);
by (rtac inverse_add_Infinitesimal_inf_close2 2);
by (auto_tac (claset() addIs [HFinite_minus_iff RS iffD1]
addSDs [Infinitesimal_minus_iff RS iffD2,
hypreal_of_real_HFinite_diff_Infinitesimal], simpset() addsimps
[hypreal_minus_inverse RS sym,hypreal_of_real_mult RS sym]));
qed "NSDERIV_inverse";
Goal "x ~= #0 ==> DERIV (%x. inverse(x)) x :> (-(inverse x ^ 2))";
by (asm_simp_tac (simpset() addsimps [NSDERIV_inverse,
NSDERIV_DERIV_iff RS sym] delsimps [thm "realpow_Suc"]) 1);
qed "DERIV_inverse";
(*--------------------------------------------------------------
Derivative of inverse
-------------------------------------------------------------*)
Goal "[| DERIV f x :> d; f(x) ~= #0 |] \
\ ==> DERIV (%x. inverse(f x)) x :> (- (d * inverse(f(x) ^ 2)))";
by (rtac (real_mult_commute RS subst) 1);
by (asm_simp_tac (simpset() addsimps [real_minus_mult_eq1,
realpow_inverse] delsimps [thm "realpow_Suc",
real_minus_mult_eq1 RS sym]) 1);
by (fold_goals_tac [o_def]);
by (blast_tac (claset() addSIs [DERIV_chain,DERIV_inverse]) 1);
qed "DERIV_inverse_fun";
Goal "[| NSDERIV f x :> d; f(x) ~= #0 |] \
\ ==> NSDERIV (%x. inverse(f x)) x :> (- (d * inverse(f(x) ^ 2)))";
by (asm_full_simp_tac (simpset() addsimps [NSDERIV_DERIV_iff,
DERIV_inverse_fun] delsimps [thm "realpow_Suc"]) 1);
qed "NSDERIV_inverse_fun";
(*--------------------------------------------------------------
Derivative of quotient
-------------------------------------------------------------*)
Goal "[| DERIV f x :> d; DERIV g x :> e; g(x) ~= #0 |] \
\ ==> DERIV (%y. f(y)*inverse(g y)) x :> (d*g(x) \
\ + -(e*f(x)))*inverse(g(x) ^ 2)";
by (dres_inst_tac [("f","g")] DERIV_inverse_fun 1);
by (dtac DERIV_mult 2);
by (REPEAT(assume_tac 1));
by (asm_full_simp_tac (simpset() addsimps [real_add_mult_distrib2,
realpow_inverse,real_minus_mult_eq1] @ real_mult_ac delsimps
[thm "realpow_Suc",real_minus_mult_eq1 RS sym,
real_minus_mult_eq2 RS sym]) 1);
qed "DERIV_quotient";
Goal "[| NSDERIV f x :> d; DERIV g x :> e; g(x) ~= #0 |] \
\ ==> NSDERIV (%y. f(y)*inverse(g y)) x :> (d*g(x) \
\ + -(e*f(x)))*inverse(g(x) ^ 2)";
by (asm_full_simp_tac (simpset() addsimps [NSDERIV_DERIV_iff,
DERIV_quotient] delsimps [thm "realpow_Suc"]) 1);
qed "NSDERIV_quotient";
(* ------------------------------------------------------------------------ *)
(* Caratheodory formulation of derivative at a point: standard proof *)
(* ------------------------------------------------------------------------ *)
Goal "(DERIV f x :> l) = \
\ (EX g. (ALL z. f z - f x = g z * (z - x)) & isCont g x & g x = l)";
by (Step_tac 1);
by (res_inst_tac
[("x","%z. if z = x then l else (f(z) - f(x)) * inverse (z - x)")] exI 1);
by (auto_tac (claset(),simpset() addsimps [real_mult_assoc,
ARITH_PROVE "z ~= x ==> z - x ~= (#0::real)"]));
by (auto_tac (claset(),simpset() addsimps [isCont_iff,DERIV_iff]));
by (ALLGOALS(rtac (LIM_equal RS iffD1)));
by (auto_tac (claset(),simpset() addsimps [real_diff_def,real_mult_assoc]));
qed "CARAT_DERIV";
Goal "NSDERIV f x :> l ==> \
\ EX g. (ALL z. f z - f x = g z * (z - x)) & isNSCont g x & g x = l";
by (auto_tac (claset(),simpset() addsimps [NSDERIV_DERIV_iff,
isNSCont_isCont_iff,CARAT_DERIV]));
qed "CARAT_NSDERIV";
(* How about a NS proof? *)
Goal "(ALL z. f z - f x = g z * (z - x)) & isNSCont g x & g x = l \
\ ==> NSDERIV f x :> l";
by (auto_tac (claset(),simpset() addsimps [NSDERIV_iff2,starfun_mult
RS sym]));
by (rtac (starfun_inverse2 RS subst) 1);
by (auto_tac (claset(),simpset() addsimps [hypreal_mult_assoc,
starfun_diff RS sym,starfun_Id]));
by (asm_full_simp_tac (simpset() addsimps [hypreal_eq_minus_iff3 RS sym,
hypreal_diff_def]) 1);
by (dtac (CLAIM_SIMP "x ~= y ==> x - y ~= (0::hypreal)" [hypreal_eq_minus_iff3 RS sym,
hypreal_diff_def]) 1);
by (asm_full_simp_tac (simpset() addsimps [isNSCont_def]) 1);
qed "CARAT_DERIVD";
(*----------------------------------------------------------------------------*)
(* Useful lemmas about nested intervals and proof by bisection (cf.Harrison) *)
(*----------------------------------------------------------------------------*)
Goal "(ALL n. (f::nat=>real) n <= f (Suc n)) --> f m <= f(m + no)";
by (induct_tac "no" 1);
by (auto_tac (claset() addIs [real_le_trans],simpset()));
qed_spec_mp "lemma_f_mono_add";
(* IMPROVE?: long proof! *)
Goal "[| ALL n. f(n) <= f(Suc n); \
\ ALL n. g(Suc n) <= g(n); \
\ ALL n. f(n) <= g(n) |] \
\ ==> EX l m. l <= m & ((ALL n. f(n) <= l) & f ----> l) & \
\ ((ALL n. m <= g(n)) & g ----> m)";
by (subgoal_tac "Bseq f" 1);
by (res_inst_tac [("k","f 0"),("K","g 0")] BseqI2 2 THEN rtac allI 2);
by (induct_tac "n" 2);
by (auto_tac (claset() addIs [real_le_trans],simpset()));
by (res_inst_tac [("j","g(Suc na)")] real_le_trans 2);
by (induct_tac "na" 3);
by (auto_tac (claset() addIs [real_le_trans],simpset()));
by (subgoal_tac "monoseq f" 1);
by (subgoal_tac "monoseq g" 1);
by (subgoal_tac "Bseq g" 1);
by (res_inst_tac [("k","f 0"),("K","g 0")] BseqI2 2 THEN rtac allI 2);
by (induct_tac "n" 2);
by (auto_tac (claset() addIs [real_le_trans],simpset()));
by (res_inst_tac [("j","f(Suc na)")] real_le_trans 2);
by (induct_tac "na" 2);
by (auto_tac (claset() addIs [real_le_trans],simpset()));
by (auto_tac (claset() addSDs [Bseq_monoseq_convergent],
simpset() addsimps [convergent_LIMSEQ_iff]));
by (res_inst_tac [("x","lim f")] exI 1);
by (res_inst_tac [("x","lim g")] exI 1);
by (auto_tac (claset() addIs [LIMSEQ_le],simpset()));
by (rtac real_leI 1 THEN rtac real_leI 2);
by (auto_tac (claset(),simpset() addsimps [LIMSEQ_iff,monoseq_Suc]));
by (ALLGOALS (dtac real_less_sum_gt_zero));
by (dres_inst_tac [("x","f n + - lim f")] spec 1);
by (rotate_tac 4 2);
by (dres_inst_tac [("x","lim g + - g n")] spec 2);
by (Step_tac 1);
by (ALLGOALS(rotate_tac 5));
by (ALLGOALS(dres_inst_tac [("x","no + n")] spec));
by (Auto_tac);
by (subgoal_tac "0 <= f(no + n) - lim f" 1);
by (induct_tac "no" 2);
by (auto_tac (claset() addIs [real_le_trans],
simpset() addsimps [real_diff_def]));
by (dtac abs_eqI1 1 THEN Asm_full_simp_tac 1);
by (dres_inst_tac [("i"," f (no + n)"),("no1","no")] (lemma_f_mono_add
RSN (2,real_less_le_trans)) 1);
by (subgoal_tac "0 <= lim g + - g(no + n)" 3);
by (induct_tac "no" 4);
by (auto_tac (claset() addIs [real_le_trans],
simpset() addsimps [real_diff_def,abs_minus_add_cancel]));
by (dtac abs_eqI1 2 THEN Asm_full_simp_tac 2);
by (dres_inst_tac [("i","- g (no + n)"),("no1","no")] (lemma_f_mono_add
RSN (2,real_less_le_trans)) 2);
by (auto_tac (claset(),simpset() addsimps [add_commute]));
qed "lemma_nest";
Goal "[| ALL n. f(n) <= f(Suc n); \
\ ALL n. g(Suc n) <= g(n); \
\ ALL n. f(n) <= g(n); \
\ (%n. f(n) - g(n)) ----> 0 |] \
\ ==> EX l. ((ALL n. f(n) <= l) & f ----> l) & \
\ ((ALL n. l <= g(n)) & g ----> l)";
by (dtac lemma_nest 1 THEN Auto_tac);
by (subgoal_tac "l = m" 1);
by (dres_inst_tac [("X","f")] LIMSEQ_diff 2);
by (auto_tac (claset() addIs [LIMSEQ_unique],simpset()));
qed "lemma_nest_unique";
Goal "EX! fn. (fn 0 = e) & (ALL n. fn (Suc n) = f n (fn n))";
by (rtac ex1I 1);
by (rtac conjI 1 THEN rtac allI 2);
by (rtac def_nat_rec_0 1 THEN rtac def_nat_rec_Suc 2);
by (Auto_tac);
by (rtac ext 1 THEN induct_tac "n" 1);
by (Auto_tac);
qed "nat_Axiom";
(****************************************************************
REPLACING THE VERSION IN REALORD.ML
****************************************************************)
(*NEW VERSION with #2*)
Goal "x < y ==> x < (x + y) / (#2::real)";
by Auto_tac;
qed "real_less_half_sum";
(*Replaces "inverse #nn" by #1/#nn *)
Addsimps [inst "x" "number_of ?w" real_inverse_eq_divide];
Goal "((x::real) = y / (#2 * z)) = (#2 * x = y/z)";
by Auto_tac;
by (dres_inst_tac [("f","%u. (#1/#2)*u")] arg_cong 1);
by Auto_tac;
qed "eq_divide_2_times_iff";
val [prem1,prem2] =
Goal "[| !!a b c. [| a <= b; b <= c; P(a,b); P(b,c)|] ==> P(a,c); \
\ ALL x. EX d::real. 0 < d & \
\ (ALL a b. a <= x & x <= b & (b - a) < d --> P(a,b)) \
\ |] ==> ALL a b. a <= b --> P(a,b)";
by (Step_tac 1);
by (cut_inst_tac [("e","(a,b)"),
("f","%n fn. if P(fst fn, (fst fn + snd fn)/#2) \
\ then ((fst fn + snd fn) /#2,snd fn) \
\ else (fst fn,(fst fn + snd fn)/#2)")]
nat_Axiom 1);
by (etac ex1E 1 THEN etac conjE 1 THEN rtac ccontr 1);
(* set up 1st premise of lemma_nest_unique *)
by (subgoal_tac "ALL n. fst((fn::nat =>(real*real)) n) <= snd (fn n)" 1);
by (rtac allI 2);
by (induct_tac "n" 2);
by (Asm_simp_tac 2);
by (dres_inst_tac [("x","na")] spec 2);
by (case_tac "P (fst (fn na), (fst (fn na) + snd (fn na)) / #2)" 2);
by (Asm_simp_tac 3);
by (Asm_simp_tac 2);
(* 2nd premise *)
by (subgoal_tac "ALL n. fst(fn n) <= fst (fn (Suc n))" 1);
by (rtac allI 2);
by (induct_tac "n" 2);
by (dres_inst_tac [("x","0")] spec 2);
by (Asm_simp_tac 3); (*super slow, but proved!*)
by (Asm_simp_tac 2);
(* 3rd premise? [lcp] *)
by (subgoal_tac "ALL n. ~P(fst(fn n),snd(fn n))" 1);
by (rtac allI 2);
by (induct_tac "n" 2);
by (Asm_simp_tac 2);
by (Asm_simp_tac 2 THEN rtac impI 2);
by (rtac ccontr 2);
by (res_inst_tac [("Pa","P (fst (fn na), snd (fn na))")] swap 2);
by (assume_tac 2);
by (res_inst_tac [("b","(fst(fn na) + snd(fn na))/#2")] prem1 2);
by (Asm_full_simp_tac 4);
by (Asm_full_simp_tac 4);
by (Asm_full_simp_tac 2);
by (Asm_simp_tac 2);
(* 3rd premise [looks like the 4th to lcp!] *)
by (subgoal_tac "ALL n. snd(fn (Suc n)) <= snd (fn n)" 1);
by (rtac allI 2);
by (induct_tac "n" 2);
by (Asm_simp_tac 2);
by (Asm_simp_tac 2);
(* FIXME: simplification takes a very long time! *)
by (ALLGOALS(thin_tac "ALL y. \
\ y 0 = (a, b) & \
\ (ALL n. \
\ y (Suc n) = \
\ (if P (fst (y n), (fst (y n) + snd (y n)) /#2) \
\ then ((fst (y n) + snd (y n)) /#2, snd (y n)) \
\ else (fst (y n),\
\ (fst (y n) + snd (y n)) /#2))) --> \
\ y = fn"));
(*another premise? the 5th? lcp*)
by (subgoal_tac "ALL n. snd(fn n) - fst(fn n) = \
\ (b - a) * inverse(#2 ^ n)" 1);
by (rtac allI 2);
by (induct_tac "n" 2);
by (Asm_simp_tac 2);
by (asm_full_simp_tac
(simpset() addsimps [eq_divide_2_times_iff, real_inverse_eq_divide,
real_diff_mult_distrib2]) 2);
(*end of the premises [lcp]*)
by (dtac lemma_nest_unique 1);
by (REPEAT(assume_tac 1));
by (Step_tac 2);
by (rtac LIMSEQ_minus_cancel 1);
by (asm_simp_tac (simpset() addsimps [CLAIM "-((a::real) - b) = (b - a)",
realpow_inverse]) 1);
by (subgoal_tac "#0 = (b-a) * #0" 1);
by (eres_inst_tac [("t","#0")] ssubst 1);
by (rtac (LIMSEQ_const RS LIMSEQ_mult) 1);
by (rtac LIMSEQ_realpow_zero 1);
by (Asm_full_simp_tac 3);
by (EVERY1[Simp_tac, Simp_tac]);
by (cut_facts_tac [prem2] 1);
by (dres_inst_tac [("x","l")] spec 1 THEN Step_tac 1);
by (rewtac LIMSEQ_def);
by (dres_inst_tac [("x","d/#2")] spec 1);
by (dres_inst_tac [("x","d/#2")] spec 1);
by (dtac real_less_half_sum 1);
by (thin_tac "ALL n. \
\ fn (Suc n) = \
\ (if P (fst (fn n), (fst (fn n) + snd (fn n))/#2) \
\ then ((fst (fn n) + snd (fn n))/#2, snd (fn n)) \
\ else (fst (fn n), \
\ (fst (fn n) + snd (fn n))/#2))" 1);
by (Step_tac 1);
by (ALLGOALS(Asm_full_simp_tac));
by (dres_inst_tac [("x","fst(fn (no + noa))")] spec 1);
by (dres_inst_tac [("x","snd(fn (no + noa))")] spec 1);
by (Step_tac 1);
by (ALLGOALS(Asm_full_simp_tac));
by (res_inst_tac [("j","abs(fst(fn(no + noa)) - l) + \
\ abs(snd(fn(no + noa)) - l)")] real_le_less_trans 1);
by (rtac (real_sum_of_halves RS subst) 2);
by (rewtac real_diff_def);
by (rtac real_add_less_mono 2);
by (Asm_full_simp_tac 2);
by (Asm_full_simp_tac 2);
by (res_inst_tac [("y1","fst(fn (no + noa)) ")]
(abs_minus_add_cancel RS subst) 1);
by (subgoal_tac "#0 <= (l + - fst (fn (no + noa)))" 1);
by (subgoal_tac "#0 <= (snd (fn (no + noa)) + - l)" 1);
by (asm_simp_tac (simpset() addsimps [abs_eqI1] @ real_add_ac) 1);
by (asm_simp_tac (simpset() addsimps real_add_ac) 1);
by (res_inst_tac [("C","l")] real_le_add_right_cancel 1);
by (res_inst_tac [("C"," fst (fn (no + noa))")] real_le_add_right_cancel 2);
by (ALLGOALS(asm_simp_tac (simpset() addsimps real_add_ac)));
qed "lemma_BOLZANO";
Goal "((ALL a b c. (a <= b & b <= c & P(a,b) & P(b,c)) --> P(a,c)) & \
\ (ALL x. EX d::real. 0 < d & \
\ (ALL a b. a <= x & x <= b & (b - a) < d --> P(a,b)))) \
\ --> (ALL a b. a <= b --> P(a,b))";
by (Step_tac 1);
by (rtac (lemma_BOLZANO RS allE) 1);
by (assume_tac 2);
by (ALLGOALS(Blast_tac));
qed "lemma_BOLZANO2";
(*----------------------------------------------------------------------------*)
(* Intermediate Value Theorem (prove contrapositive by bisection) *)
(*----------------------------------------------------------------------------*)
Goal "[| f(a) <= y & y <= f(b); \
\ a <= b; \
\ (ALL x. a <= x & x <= b --> isCont f x) \
\ |] ==> EX x. a <= x & x <= b & f(x) = y";
by (rtac contrapos_pp 1);
by (assume_tac 1);
by (cut_inst_tac [("P","%(u,v). a <= u & u <= v & v <= b --> \
\ ~(f(u) <= y & y <= f(v))")] lemma_BOLZANO2 1);
by (Step_tac 1);
by (ALLGOALS(Asm_full_simp_tac));
by (Blast_tac 2);
by (asm_full_simp_tac (simpset() addsimps [isCont_iff,LIM_def]) 1);
by (rtac ccontr 1);
by (subgoal_tac "a <= x & x <= b" 1);
by (Asm_full_simp_tac 2);
by (rotate_tac 3 2);
by (dres_inst_tac [("x","1r")] spec 2);
by (Step_tac 2);
by (Asm_full_simp_tac 2);
by (Asm_full_simp_tac 2);
by (REPEAT(blast_tac (claset() addIs [real_le_trans]) 2));
by (REPEAT(dres_inst_tac [("x","x")] spec 1));
by (Asm_full_simp_tac 1);
(**)
by (rotate_tac 4 1);
by (dres_inst_tac [("x","abs(y - f x)")] spec 1);
by (Step_tac 1);
by (asm_full_simp_tac (simpset() addsimps [real_less_le,
abs_ge_zero,real_diff_def]) 1);
by (dtac (sym RS (abs_zero_iff RS iffD2)) 1);
by (arith_tac 1);
by (dres_inst_tac [("x","s")] spec 1);
by (Step_tac 1);
by (cut_inst_tac [("R1.0","f x"),("R2.0","y")] real_linear 1);
by (Auto_tac);
by (dres_inst_tac [("x","ba - x")] spec 1);
by (auto_tac (claset(),
simpset()
addsimps [abs_iff, real_diff_le_eq,
(real_diff_def RS meta_eq_to_obj_eq) RS sym,
real_less_le_iff, real_le_diff_eq,
CLAIM "(~(x::real) <= y) = (y < x)",
CLAIM "(-x < -y) = ((y::real) < x)",
CLAIM "(-(y - x)) = (x - (y::real))",
CLAIM "(x-y=#0) = (x = (y::real))"]));
by (dres_inst_tac [("x","aa - x")] spec 1);
by (case_tac "x <= aa" 1);
by (auto_tac (claset(),simpset() addsimps [real_minus_zero_le_iff2,
real_le_diff_eq,real_diff_le_eq,(real_le_def RS meta_eq_to_obj_eq)
RS sym]));
by (dres_inst_tac [("z","x"),("w","aa")] real_le_anti_sym 1);
by (assume_tac 1 THEN Asm_full_simp_tac 1);
qed "IVT";
Goal "[| f(b) <= y & y <= f(a); \
\ a <= b; \
\ (ALL x. a <= x & x <= b --> isCont f x) \
\ |] ==> EX x. a <= x & x <= b & f(x) = y";
by (subgoal_tac "- f a <= -y & -y <= - f b" 1);
by (thin_tac "f b <= y & y <= f a" 1);
by (dres_inst_tac [("f","%x. - f x")] IVT 1);
by (auto_tac (claset() addIs [isCont_minus],simpset()));
qed "IVT2";
Goal "(f(a) <= y & y <= f(b) & a <= b & \
\ (ALL x. a <= x & x <= b --> isCont f x)) \
\ --> (EX x. a <= x & x <= b & f(x) = y)";
by (blast_tac (claset() addIs [IVT]) 1);
qed "IVT_objl";
Goal "(f(b) <= y & y <= f(a) & a <= b & \
\ (ALL x. a <= x & x <= b --> isCont f x)) \
\ --> (EX x. a <= x & x <= b & f(x) = y)";
by (blast_tac (claset() addIs [IVT2]) 1);
qed "IVT2_objl";
(*----------------------------------------------------------------------------*)
(* By bisection, function continuous on closed interval is bounded above *)
(*----------------------------------------------------------------------------*)
Goal "abs (real_of_nat x) = real_of_nat x";
by (auto_tac (claset() addIs [abs_eqI1],simpset()));
qed "abs_real_of_nat_cancel";
Addsimps [abs_real_of_nat_cancel];
Goal "~ abs(x) + 1r < x";
by (rtac real_leD 1);
by (auto_tac (claset() addIs [abs_ge_self RS real_le_trans],simpset()));
qed "abs_add_one_not_less_self";
Addsimps [abs_add_one_not_less_self];
Goal "[| a <= b; ALL x. a <= x & x <= b --> isCont f x |]\
\ ==> EX M. ALL x. a <= x & x <= b --> f(x) <= M";
by (cut_inst_tac [("P","%(u,v). a <= u & u <= v & v <= b --> \
\ (EX M. ALL x. u <= x & x <= v --> f x <= M)")]
lemma_BOLZANO2 1);
by (Step_tac 1);
by (ALLGOALS(Asm_full_simp_tac));
by (cut_inst_tac [("x","M"),("y","Ma")]
(CLAIM "x <= y | y <= (x::real)") 1);
by (Step_tac 1);
by (res_inst_tac [("x","Ma")] exI 1);
by (Step_tac 1);
by (cut_inst_tac [("x","xb"),("y","xa")]
(CLAIM "x <= y | y <= (x::real)") 1);
by (Step_tac 1);
by (rtac real_le_trans 1 THEN assume_tac 2);
by (Asm_full_simp_tac 1);
by (Asm_full_simp_tac 1);
by (res_inst_tac [("x","M")] exI 1);
by (Step_tac 1);
by (cut_inst_tac [("x","xb"),("y","xa")]
(CLAIM "x <= y | y <= (x::real)") 1);
by (Step_tac 1);
by (Asm_full_simp_tac 1);
by (rtac real_le_trans 1 THEN assume_tac 2);
by (Asm_full_simp_tac 1);
by (case_tac "a <= x & x <= b" 1);
by (res_inst_tac [("x","#1")] exI 2);
by (auto_tac (claset(),
simpset() addsimps [LIM_def,isCont_iff]));
by (dres_inst_tac [("x","x")] spec 1 THEN Auto_tac);
by (thin_tac "ALL M. EX x. a <= x & x <= b & ~ f x <= M" 1);
by (dres_inst_tac [("x","#1")] spec 1);
by Auto_tac;
by (res_inst_tac [("x","s")] exI 1 THEN Auto_tac);
by (res_inst_tac [("x","abs(f x) + #1")] exI 1 THEN Step_tac 1);
by (dres_inst_tac [("x","xa - x")] spec 1 THEN Auto_tac);
by (res_inst_tac [("j","abs(f xa)")] real_le_trans 3);
by (res_inst_tac [("j","abs(f x) + abs(f(xa) - f(x))")] real_le_trans 4);
by (auto_tac (claset() addIs [abs_triangle_ineq RSN (2, real_le_trans)],
simpset() addsimps [real_diff_def,abs_ge_self]));
(*arith_tac problem: this step should not be needed*)
by (asm_full_simp_tac (simpset() addsimps [rename_numerals (real_eq_minus_iff2 RS sym)]) 1);
by (auto_tac (claset(),
simpset() addsimps [abs_real_def] addsplits [split_if_asm]));
qed "isCont_bounded";
(*----------------------------------------------------------------------------*)
(* Refine the above to existence of least upper bound *)
(*----------------------------------------------------------------------------*)
Goal "((EX x. x : S) & (EX y. isUb UNIV S (y::real))) --> \
\ (EX t. isLub UNIV S t)";
by (blast_tac (claset() addIs [reals_complete]) 1);
qed "lemma_reals_complete";
Goal "[| a <= b; ALL x. a <= x & x <= b --> isCont f x |] \
\ ==> EX M. (ALL x. a <= x & x <= b --> f(x) <= M) & \
\ (ALL N. N < M --> (EX x. a <= x & x <= b & N < f(x)))";
by (cut_inst_tac [("S","Collect (%y. EX x. a <= x & x <= b & y = f x)")]
lemma_reals_complete 1);
by (Auto_tac);
by (dtac isCont_bounded 1 THEN assume_tac 1);
by (auto_tac (claset(),simpset() addsimps [isUb_def,leastP_def,
isLub_def,setge_def,setle_def]));
by (rtac exI 1 THEN Auto_tac);
by (REPEAT(dtac spec 1) THEN Auto_tac);
by (dres_inst_tac [("x","x")] spec 1);
by (auto_tac (claset() addSIs [real_leI],simpset()));
qed "isCont_has_Ub";
(*----------------------------------------------------------------------------*)
(* Now show that it attains its upper bound *)
(*----------------------------------------------------------------------------*)
Goal "[| a <= b; ALL x. a <= x & x <= b --> isCont f x |] \
\ ==> EX M. (ALL x. a <= x & x <= b --> f(x) <= M) & \
\ (EX x. a <= x & x <= b & f(x) = M)";
by (ftac isCont_has_Ub 1 THEN assume_tac 1);
by (Clarify_tac 1);
by (res_inst_tac [("x","M")] exI 1);
by (Asm_full_simp_tac 1);
by (rtac ccontr 1);
by (subgoal_tac "ALL x. a <= x & x <= b --> f x < M" 1 THEN Step_tac 1);
by (rtac ccontr 2 THEN dtac real_leI 2);
by (dres_inst_tac [("z","M")] real_le_anti_sym 2);
by (REPEAT(Blast_tac 2));
by (subgoal_tac "ALL x. a <= x & x <= b --> isCont (%x. inverse(M - f x)) x" 1);
by (Step_tac 1);
by (EVERY[rtac isCont_inverse 2, rtac isCont_diff 2, rtac notI 4]);
by (ALLGOALS(asm_full_simp_tac (simpset() addsimps [real_diff_eq_eq])));
by (Blast_tac 2);
by (subgoal_tac
"EX k. ALL x. a <= x & x <= b --> (%x. inverse(M - (f x))) x <= k" 1);
by (rtac isCont_bounded 2);
by (Step_tac 1);
by (subgoal_tac "ALL x. a <= x & x <= b --> #0 < inverse(M - f(x))" 1);
by (Asm_full_simp_tac 1);
by (Step_tac 1);
by (asm_full_simp_tac (simpset() addsimps [real_less_diff_eq]) 2);
by (subgoal_tac
"ALL x. a <= x & x <= b --> (%x. inverse(M - (f x))) x < (k + #1)" 1);
by (Step_tac 1);
by (res_inst_tac [("j","k")] real_le_less_trans 2);
by (asm_full_simp_tac (simpset() addsimps [real_zero_less_one]) 3);
by (Asm_full_simp_tac 2);
by (subgoal_tac "ALL x. a <= x & x <= b --> \
\ inverse(k + #1) < inverse((%x. inverse(M - (f x))) x)" 1);
by (Step_tac 1);
by (rtac real_inverse_less_swap 2);
by (ALLGOALS Asm_full_simp_tac);
by (dres_inst_tac [("P", "%N. N<M --> ?Q N"),
("x","M - inverse(k + #1)")] spec 1);
by (Step_tac 1 THEN dtac real_leI 1);
by (dtac (real_le_diff_eq RS iffD1) 1);
by (REPEAT(dres_inst_tac [("x","a")] spec 1));
by (Asm_full_simp_tac 1);
by (asm_full_simp_tac
(simpset() addsimps [real_inverse_eq_divide, pos_real_divide_le_eq]) 1);
by (cut_inst_tac [("x","k"),("y","M-f a")] real_0_less_mult_iff 1);
by (Asm_full_simp_tac 1);
(*last one*)
by (REPEAT(dres_inst_tac [("x","x")] spec 1));
by (Asm_full_simp_tac 1);
qed "isCont_eq_Ub";
(*----------------------------------------------------------------------------*)
(* Same theorem for lower bound *)
(*----------------------------------------------------------------------------*)
Goal "[| a <= b; ALL x. a <= x & x <= b --> isCont f x |] \
\ ==> EX M. (ALL x. a <= x & x <= b --> M <= f(x)) & \
\ (EX x. a <= x & x <= b & f(x) = M)";
by (subgoal_tac "ALL x. a <= x & x <= b --> isCont (%x. -(f x)) x" 1);
by (blast_tac (claset() addIs [isCont_minus]) 2);
by (dres_inst_tac [("f","(%x. -(f x))")] isCont_eq_Ub 1);
by (Step_tac 1);
by (Auto_tac);
qed "isCont_eq_Lb";
(* ------------------------------------------------------------------------- *)
(* Another version. *)
(* ------------------------------------------------------------------------- *)
Goal "[|a <= b; ALL x. a <= x & x <= b --> isCont f x |] \
\ ==> EX L M. (ALL x. a <= x & x <= b --> L <= f(x) & f(x) <= M) & \
\ (ALL y. L <= y & y <= M --> (EX x. a <= x & x <= b & (f(x) = y)))";
by (ftac isCont_eq_Lb 1);
by (ftac isCont_eq_Ub 2);
by (REPEAT(assume_tac 1));
by (Step_tac 1);
by (res_inst_tac [("x","f x")] exI 1);
by (res_inst_tac [("x","f xa")] exI 1);
by (Asm_full_simp_tac 1);
by (Step_tac 1);
by (cut_inst_tac [("x","x"),("y","xa")] (CLAIM "x <= y | y <= (x::real)") 1);
by (Step_tac 1);
by (cut_inst_tac [("f","f"),("a","x"),("b","xa"),("y","y")] IVT_objl 1);
by (cut_inst_tac [("f","f"),("a","xa"),("b","x"),("y","y")] IVT2_objl 2);
by (Step_tac 1);
by (res_inst_tac [("x","xb")] exI 2);
by (res_inst_tac [("x","xb")] exI 4);
by (ALLGOALS(Asm_full_simp_tac));
qed "isCont_Lb_Ub";
(*----------------------------------------------------------------------------*)
(* If f'(x) > 0 then x is locally strictly increasing at the right *)
(*----------------------------------------------------------------------------*)
(**????????????????????????????????????????????????????????????????
MOVE EARLIER *)
(** The next several equations can make the simplifier loop! **)
Goal "(x < - y) = (y < - (x::real))";
by Auto_tac;
qed "real_less_minus";
Goal "(- x < y) = (- y < (x::real))";
by Auto_tac;
(*or this:
by (res_inst_tac [("t","x")] (real_minus_minus RS subst) 1);
by (stac real_minus_less_minus 1);
by (Simp_tac 1);
*)
qed "real_minus_less";
Goal "(x <= - y) = (y <= - (x::real))";
by Auto_tac;
qed "real_le_minus";
Goal "(- x <= y) = (- y <= (x::real))";
by Auto_tac;
qed "real_minus_le";
Goal "(x = - y) = (y = - (x::real))";
by Auto_tac;
qed "real_equation_minus";
Goal "(- x = y) = (- (y::real) = x)";
by Auto_tac;
qed "real_minus_equation";
(*Distributive laws for literals*)
Addsimps (map (inst "w" "number_of ?v")
[real_add_mult_distrib, real_add_mult_distrib2,
real_diff_mult_distrib, real_diff_mult_distrib2]);
Addsimps (map (inst "x" "number_of ?v")
[real_less_minus, real_le_minus, real_equation_minus]);
Addsimps (map (inst "y" "number_of ?v")
[real_minus_less, real_minus_le, real_minus_equation]);
(*move up these rewrites AFTER the rest works*)
Goal "(x+y = (#0::real)) = (y = -x)";
by Auto_tac;
qed "real_add_eq_0_iff";
AddIffs [real_add_eq_0_iff];
Goal "((#0::real) = x+y) = (y = -x)";
by Auto_tac;
qed "real_0_eq_add_iff";
AddIffs [real_0_eq_add_iff];
Goal "(x+y < (#0::real)) = (y < -x)";
by Auto_tac;
qed "real_add_less_0_iff";
AddIffs [real_add_less_0_iff];
Goal "((#0::real) < x+y) = (-x < y)";
by Auto_tac;
qed "real_0_less_add_iff";
AddIffs [real_0_less_add_iff];
Goal "(x+y <= (#0::real)) = (y <= -x)";
by Auto_tac;
qed "real_add_le_0_iff";
AddIffs [real_add_le_0_iff];
Goal "((#0::real) <= x+y) = (-x <= y)";
by Auto_tac;
qed "real_0_le_add_iff";
AddIffs [real_0_le_add_iff];
(*
Addsimps [symmetric real_diff_def];
*)
Goalw [deriv_def,LIM_def]
"[| DERIV f x :> l; #0 < l |] ==> \
\ EX d. #0 < d & (ALL h. #0 < h & h < d --> f(x) < f(x + h))";
by (dtac spec 1 THEN Auto_tac);
by (res_inst_tac [("x","s")] exI 1 THEN Auto_tac);
by (subgoal_tac "#0 < l*h" 1);
by (asm_full_simp_tac (simpset() addsimps [real_0_less_mult_iff]) 2);
by (dres_inst_tac [("x","h")] spec 1);
by (asm_full_simp_tac
(simpset() addsimps [abs_real_def, real_inverse_eq_divide,
pos_real_le_divide_eq, pos_real_less_divide_eq]
addsplits [split_if_asm]) 1);
qed "DERIV_left_inc";
Addsimps [real_minus_less_minus] (****************);
Goal "-(x-y) = y - (x::real)";
by (arith_tac 1);
qed "real_minus_diff_eq";
Addsimps [real_minus_diff_eq]; (******************************************************************)
Goalw [deriv_def,LIM_def]
"[| DERIV f x :> l; l < #0 |] ==> \
\ EX d. #0 < d & (ALL h. #0 < h & h < d --> f(x) < f(x - h))";
by (dres_inst_tac [("x","-l")] spec 1 THEN Auto_tac);
by (res_inst_tac [("x","s")] exI 1 THEN Auto_tac);
by (subgoal_tac "l*h < #0" 1);
by (asm_full_simp_tac (simpset() addsimps [real_mult_less_0_iff]) 2);
by (dres_inst_tac [("x","-h")] spec 1);
by (asm_full_simp_tac
(simpset() addsimps [abs_real_def, real_inverse_eq_divide,
pos_real_less_divide_eq,
symmetric real_diff_def]
addsplits [split_if_asm]) 1);
by (subgoal_tac "#0 < (f (x - h) - f x)/h" 1);
by (arith_tac 2);
by (asm_full_simp_tac
(simpset() addsimps [pos_real_less_divide_eq]) 1);
qed "DERIV_left_dec";
Goal "[| DERIV f x :> l; \
\ EX d. #0 < d & (ALL y. abs(x - y) < d --> f(y) <= f(x)) |] \
\ ==> l = #0";
by (res_inst_tac [("R1.0","l"),("R2.0","#0")] real_linear_less2 1);
by (Step_tac 1);
by (dtac DERIV_left_dec 1);
by (dtac DERIV_left_inc 3);
by (Step_tac 1);
by (dres_inst_tac [("d1.0","d"),("d2.0","da")] real_lbound_gt_zero 1);
by (dres_inst_tac [("d1.0","d"),("d2.0","da")] real_lbound_gt_zero 3);
by (Step_tac 1);
by (dres_inst_tac [("x","x - e")] spec 1);
by (dres_inst_tac [("x","x + e")] spec 2);
by (auto_tac (claset(),simpset() addsimps [abs_eqI2,abs_minus_cancel]));
qed "DERIV_local_max";
(*----------------------------------------------------------------------------*)
(* Similar theorem for a local minimum *)
(*----------------------------------------------------------------------------*)
Goal "[| DERIV f x :> l; \
\ EX d::real. #0 < d & (ALL y. abs(x - y) < d --> f(x) <= f(y)) |] \
\ ==> l = #0";
by (dtac (DERIV_minus RS DERIV_local_max) 1);
by Auto_tac;
qed "DERIV_local_min";
(*----------------------------------------------------------------------------*)
(* In particular if a function is locally flat *)
(*----------------------------------------------------------------------------*)
Goal "[| DERIV f x :> l; \
\ EX d. #0 < d & (ALL y. abs(x - y) < d --> f(x) = f(y)) |] \
\ ==> l = #0";
by (auto_tac (claset() addSDs [DERIV_local_max],simpset()));
qed "DERIV_local_const";
(*----------------------------------------------------------------------------*)
(* Lemma about introducing open ball in open interval *)
(*----------------------------------------------------------------------------*)
Goal "[| a < x; x < b |] ==> \
\ EX d::real. #0 < d & (ALL y. abs(x - y) < d --> a < y & y < b)";
by (simp_tac (simpset() addsimps [abs_interval_iff]) 1);
by (cut_inst_tac [("x","x - a"),("y","b - x")]
(CLAIM "x <= y | y <= (x::real)") 1);
by (Step_tac 1);
by (res_inst_tac [("x","x - a")] exI 1);
by (res_inst_tac [("x","b - x")] exI 2);
by (Auto_tac);
by (auto_tac (claset(),simpset() addsimps [real_less_diff_eq]));
qed "lemma_interval_lt";
Goal "[| a < x; x < b |] ==> \
\ EX d::real. #0 < d & (ALL y. abs(x - y) < d --> a <= y & y <= b)";
by (dtac lemma_interval_lt 1);
by (Auto_tac);
by (auto_tac (claset() addSIs [exI] ,simpset()));
qed "lemma_interval";
(*-----------------------------------------------------------------------
Rolle's Theorem
If f is defined and continuous on the finite closed interval [a,b]
and differentiable a least on the open interval (a,b), and f(a) = f(b),
then x0 : (a,b) such that f'(x0) = #0
----------------------------------------------------------------------*)
Goal "[| a < b; f(a) = f(b); \
\ ALL x. a <= x & x <= b --> isCont f x; \
\ ALL x. a < x & x < b --> f differentiable x \
\ |] ==> EX z. a < z & z < b & DERIV f z :> #0";
by (ftac (real_less_imp_le RS isCont_eq_Ub) 1);
by (EVERY1[assume_tac,Step_tac]);
by (ftac (real_less_imp_le RS isCont_eq_Lb) 1);
by (EVERY1[assume_tac,Step_tac]);
by (case_tac "a < x & x < b" 1 THEN etac conjE 1);
by (Asm_full_simp_tac 2);
by (forw_inst_tac [("a","a"),("x","x")] lemma_interval 1);
by (EVERY1[assume_tac,etac exE]);
by (res_inst_tac [("x","x")] exI 1 THEN Asm_full_simp_tac 1);
by (subgoal_tac "(EX l. DERIV f x :> l) & \
\ (EX d. #0 < d & (ALL y. abs(x - y) < d --> f(y) <= f(x)))" 1);
by (Clarify_tac 1 THEN rtac conjI 2);
by (blast_tac (claset() addIs [differentiableD]) 2);
by (Blast_tac 2);
by (ftac DERIV_local_max 1);
by (EVERY1[Blast_tac,Blast_tac]);
by (case_tac "a < xa & xa < b" 1 THEN etac conjE 1);
by (Asm_full_simp_tac 2);
by (forw_inst_tac [("a","a"),("x","xa")] lemma_interval 1);
by (EVERY1[assume_tac,etac exE]);
by (res_inst_tac [("x","xa")] exI 1 THEN Asm_full_simp_tac 1);
by (subgoal_tac "(EX l. DERIV f xa :> l) & \
\ (EX d. #0 < d & (ALL y. abs(xa - y) < d --> f(xa) <= f(y)))" 1);
by (Clarify_tac 1 THEN rtac conjI 2);
by (blast_tac (claset() addIs [differentiableD]) 2);
by (Blast_tac 2);
by (ftac DERIV_local_min 1);
by (EVERY1[Blast_tac,Blast_tac]);
by (subgoal_tac "ALL x. a <= x & x <= b --> f(x) = f(b)" 1);
by (Clarify_tac 2);
by (rtac real_le_anti_sym 2);
by (subgoal_tac "f b = f x" 2);
by (Asm_full_simp_tac 2);
by (res_inst_tac [("x1","a"),("y1","x")] (real_le_imp_less_or_eq RS disjE) 2);
by (assume_tac 2);
by (dres_inst_tac [("z","x"),("w","b")] real_le_anti_sym 2);
by (subgoal_tac "f b = f xa" 5);
by (Asm_full_simp_tac 5);
by (res_inst_tac [("x1","a"),("y1","xa")] (real_le_imp_less_or_eq RS disjE) 5);
by (assume_tac 5);
by (dres_inst_tac [("z","xa"),("w","b")] real_le_anti_sym 5);
by (REPEAT(Asm_full_simp_tac 2));
by (dtac real_dense 1 THEN etac exE 1);
by (res_inst_tac [("x","r")] exI 1 THEN Asm_full_simp_tac 1);
by (etac conjE 1);
by (forw_inst_tac [("a","a"),("x","r")] lemma_interval 1);
by (EVERY1[assume_tac, etac exE]);
by (subgoal_tac "(EX l. DERIV f r :> l) & \
\ (EX d. #0 < d & (ALL y. abs(r - y) < d --> f(r) = f(y)))" 1);
by (Clarify_tac 1 THEN rtac conjI 2);
by (blast_tac (claset() addIs [differentiableD]) 2);
by (EVERY1[ftac DERIV_local_const, Blast_tac, Blast_tac]);
by (res_inst_tac [("x","d")] exI 1);
by (EVERY1[rtac conjI, Blast_tac, rtac allI, rtac impI]);
by (res_inst_tac [("s","f b")] trans 1);
by (blast_tac (claset() addSDs [real_less_imp_le]) 1);
by (rtac sym 1 THEN Blast_tac 1);
qed "Rolle";
(*----------------------------------------------------------------------------*)
(* Mean value theorem *)
(*----------------------------------------------------------------------------*)
(*????????????????*)
Goal "k~=#0 ==> (k*m) / k = (m::real)";
by (dres_inst_tac [("n","#1")] real_mult_div_cancel1 1);
by (Asm_full_simp_tac 1);
qed "real_mult_div_self1";
Addsimps [real_mult_div_self1];
(*move up these rewrites AFTER the rest works*)
Goal "(x-y = (#0::real)) = (x = y)";
by Auto_tac;
qed "real_diff_eq_0_iff";
AddIffs [real_diff_eq_0_iff];
Goal "((#0::real) = x-y) = (x = y)";
by Auto_tac;
qed "real_0_eq_diff_iff";
AddIffs [real_0_eq_diff_iff];
Goal "(x-y < (#0::real)) = (x < y)";
by Auto_tac;
qed "real_diff_less_0_iff";
AddIffs [real_diff_less_0_iff];
Goal "((#0::real) < x-y) = (y < x)";
by Auto_tac;
qed "real_0_less_diff_iff";
AddIffs [real_0_less_diff_iff];
Goal "(x-y <= (#0::real)) = (x <= y)";
by Auto_tac;
qed "real_diff_le_0_iff";
AddIffs [real_diff_le_0_iff];
Goal "((#0::real) <= x-y) = (y <= x)";
by Auto_tac;
qed "real_0_le_diff_iff";
AddIffs [real_0_le_diff_iff];
Goal "f a - (f b - f a)/(b - a) * a = \
\ f b - (f b - f a)/(b - a) * (b::real)";
by (case_tac "a = b" 1);
by (asm_full_simp_tac (simpset() addsimps [REAL_DIVIDE_ZERO]) 1);
by (res_inst_tac [("c1","b - a")] (real_mult_left_cancel RS iffD1) 1);
by (arith_tac 1);
by (auto_tac (claset(),
simpset() addsimps [real_diff_mult_distrib2, real_diff_eq_eq,
eq_commute]));
by (auto_tac (claset(),
simpset() addsimps [real_diff_mult_distrib2, real_mult_commute]));
qed "lemma_MVT";