src/HOL/Real/Hyperreal/Lim.ML

final tuning;

(*  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]);

(*---------------------------------------------------------------
   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. (#0 < abs(x + -a) & (abs(x + -a) < s) \
\          --> abs(f x + -L) < r))))";
by (Blast_tac 1);
qed "LIM_iff";

Goalw [LIM_def] 
      "!!a. [| f -- a --> L; #0 < r |] \
\           ==> (EX s. #0 < s & (ALL x. (#0 < abs(x + -a) \
\           & (abs(x + -a) < s) --> abs(f x + -L) < r)))";
by (Blast_tac 1);
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*rinv(#1 + #1)")] spec 1));
by (dtac (rename_numerals (real_zero_less_two RS real_rinv_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";

Goal "(#0::real) < abs (x + -a) ==> x ~= a";
by (arith_tac 1);
qed "lemma_rabs_not_eq";

(*--------------------------------------------------------------
   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 [lemma_rabs_not_eq]));
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 [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. (#0::real) < abs ((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 THEN arith_tac 1);
qed "LIM_NSLIM";
 
(*---------------------------------------------------------------------
    Limit: NS definition ==> standard definition
 ---------------------------------------------------------------------*)

Goal "ALL s. #0 < s --> (EX xa.  #0 < abs (xa + - x) & \
\        abs (xa + - x) < s  & r <= abs (f xa + -L)) \
\     ==> ALL n::nat. EX xa.  #0 < abs (xa + - x) & \
\             abs(xa + -x) < rinv(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_rinv_gt_zero) 1);
by Auto_tac;
val lemma_LIM = result();

Goal "ALL s. #0 < s --> (EX xa.  #0 < abs (xa + - x) & \
\        abs (xa + - x) < s  & r <= abs (f xa + -L)) \
\     ==> EX X. ALL n::nat. #0 < abs (X n + - x) & \
\               abs(X n + -x) < rinv(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 "{n. f (X n) + - L = Y n} Int \
\         {n. #0 < abs (X n + - x) & \
\             abs (X n + - x) < rinv (real_of_posnat  n) & \
\             r <= abs (f (X n) + - L)} <= \
\         {n. r <= abs (Y n)}";
by (Auto_tac);
val lemma_Int = result ();

Goal "!!X. ALL n. #0 < abs (X n + - x) & \
\         abs (X n + - x) < rinv (real_of_posnat  n) & \
\         r <= abs (f (X n) + - L) ==> \
\         ALL n. abs (X n + - x) < rinv (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 FreeUltrafilterNat_Ex_P 1 THEN etac exE 1);
by (dres_inst_tac [("x","n")] spec 1);
by (asm_full_simp_tac (simpset() addsimps 
    [real_add_minus,real_less_not_refl]) 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 (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_rinv
 -----------------------------*)
Goalw [NSLIM_def] 
      "!!f. [| f -- a --NS> L; \
\              L ~= #0 \
\           |] ==> (%x. rinv(f(x))) -- a --NS> (rinv 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_hrinv RS sym]));
by (forward_tac [inf_close_hypreal_of_real_not_zero] 1 
    THEN assume_tac 1);
by (auto_tac (claset() addSEs [(starfun_hrinv2 RS subst),
    inf_close_hrinv,hypreal_of_real_HFinite_diff_Infinitesimal],
    simpset()));
qed "NSLIM_rinv";

Goal "[| f -- a --> L; \
\        L ~= #0 |] ==> (%x. rinv(f(x))) -- a --> (rinv L)";
by (asm_full_simp_tac (simpset() addsimps [LIM_NSLIM_iff,
    NSLIM_rinv]) 1);
qed "LIM_rinv";

(*------------------------------
    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. rinv (f x)) x";
by (blast_tac (claset() addIs [LIM_rinv]) 1);
qed "isCont_rinv";

Goal "[| isNSCont f x; f x ~= #0 |] ==> isNSCont (%x. rinv (f x)) x";
by (auto_tac (claset() addIs [isCont_rinv],simpset() addsimps 
    [isNSCont_isCont_iff]));
qed "isNSCont_rinv";

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 (Fast_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) < rinv(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_rinv_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)) < rinv(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) < rinv (real_of_posnat  n) & \
\         r <= abs (f (X n) + - f(Y n)) ==> \
\         ALL n. abs (X n + - Y n) < rinv (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) < rinv (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))*rinv(h)) -- #0 --> D)";
by (Blast_tac 1);        
qed "DERIV_iff";

Goalw [deriv_def] 
      "(DERIV f x :> D) = ((%h. (f(x + h) + - f(x))*rinv(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))*rinv(h)) -- #0 --> D";
by (Blast_tac 1);        
qed "DERIVD";

Goalw [deriv_def] "DERIV f x :> D ==> \
\          (%h. (f(x + h) + - f(x))*rinv(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))*rinv(h)) -- #0 --> D) = \
\ ((%x. (f(x) + -f(a))*rinv(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))*rinv(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))*rinv(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_rinv_hrinv,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))*rinv(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) * rinv (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_hrinv2 RS sym) 2);
by (auto_tac (claset() addDs [hypreal_mult_hrinv_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) * hrinv 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) * hrinv 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_rinv_hrinv,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)) * hrinv 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)))* \
\                  hrinv ((*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_hrinv3]));
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)) * \
\                     hrinv xa @= hypreal_of_real(Db)";
by (auto_tac (claset(),simpset() addsimps [NSDERIV_NSLIM_iff,
    NSLIM_def,starfun_mult RS sym,starfun_rinv_hrinv,
    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_rinv_hrinv,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","hrinv 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_rinv_hrinv,hypreal_of_real_one] 
    @ real_add_ac));
qed "NSDERIV_Id";
Addsimps [NSDERIV_Id];

Goal "DERIV (%x. x) x :> #1";
by (simp_tac (simpset() addsimps [NSDERIV_DERIV_iff RS sym]) 1);
qed "DERIV_Id";
Addsimps [DERIV_Id];

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. rinv(x)) x :> (- (rinv 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_rinv_hrinv,
         hypreal_of_real_hrinv 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_hrinv_add,
         hrinv_mult_eq RS sym, hypreal_minus_hrinv 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"," hrinv(- hypreal_of_real x * hypreal_of_real x)")] inf_close_trans 2);
by (rtac hrinv_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_hrinv RS sym,hypreal_of_real_mult RS sym]));
qed "NSDERIV_rinv";

Goal "x ~= #0 ==> DERIV (%x. rinv(x)) x :> (-(rinv x ^ 2))";
by (asm_simp_tac (simpset() addsimps [NSDERIV_rinv,
         NSDERIV_DERIV_iff RS sym] delsimps [thm "realpow_Suc"]) 1);
qed "DERIV_rinv";

(*--------------------------------------------------------------
        Derivative of inverse 
 -------------------------------------------------------------*)
Goal "[| DERIV f x :> d; f(x) ~= #0 |] \
\     ==> DERIV (%x. rinv(f x)) x :> (- (d * rinv(f(x) ^ 2)))";
by (rtac (real_mult_commute RS subst) 1);
by (asm_simp_tac (simpset() addsimps [real_minus_mult_eq1,
    realpow_rinv] 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_rinv]) 1);
qed "DERIV_rinv_fun";

Goal "[| NSDERIV f x :> d; f(x) ~= #0 |] \
\     ==> NSDERIV (%x. rinv(f x)) x :> (- (d * rinv(f(x) ^ 2)))";
by (asm_full_simp_tac (simpset() addsimps [NSDERIV_DERIV_iff,
            DERIV_rinv_fun] delsimps [thm "realpow_Suc"]) 1);
qed "NSDERIV_rinv_fun";

(*--------------------------------------------------------------
        Derivative of quotient 
 -------------------------------------------------------------*)
Goal "[| DERIV f x :> d; DERIV g x :> e; g(x) ~= #0 |] \
\      ==> DERIV (%y. f(y)*rinv(g y)) x :> (d*g(x) \
\                           + -(e*f(x)))*rinv(g(x) ^ 2)";
by (dres_inst_tac [("f","g")] DERIV_rinv_fun 1);
by (dtac DERIV_mult 2);
by (REPEAT(assume_tac 1));
by (asm_full_simp_tac (simpset() addsimps [real_add_mult_distrib2,
        realpow_rinv,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)*rinv(g y)) x :> (d*g(x) \
\                           + -(e*f(x)))*rinv(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)) * rinv (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_hrinv2 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";
 
(*--------------------------------------------------------------------*)
(* In this theory, still have to include Bisection theorem, IVT, MVT, *)
(* Rolle etc.                                                         *)
(*--------------------------------------------------------------------*)