--- a/src/HOL/Analysis/Weierstrass_Theorems.thy Sat Oct 03 23:01:40 2020 +0100
+++ b/src/HOL/Analysis/Weierstrass_Theorems.thy Mon Oct 05 12:47:19 2020 +0100
@@ -9,7 +9,7 @@
subsection \<open>Bernstein polynomials\<close>
definition\<^marker>\<open>tag important\<close> Bernstein :: "[nat,nat,real] \<Rightarrow> real" where
- "Bernstein n k x \<equiv> of_nat (n choose k) * x ^ k * (1 - x) ^ (n - k)"
+ "Bernstein n k x \<equiv> of_nat (n choose k) * x^k * (1 - x)^(n - k)"
lemma Bernstein_nonneg: "\<lbrakk>0 \<le> x; x \<le> 1\<rbrakk> \<Longrightarrow> 0 \<le> Bernstein n k x"
by (simp add: Bernstein_def)
@@ -22,7 +22,7 @@
by (simp add: Bernstein_def)
lemma binomial_deriv1:
- "(\<Sum>k\<le>n. (of_nat k * of_nat (n choose k)) * a^(k-1) * b^(n-k)) = real_of_nat n * (a+b) ^ (n-1)"
+ "(\<Sum>k\<le>n. (of_nat k * of_nat (n choose k)) * a^(k-1) * b^(n-k)) = real_of_nat n * (a+b)^(n-1)"
apply (rule DERIV_unique [where f = "\<lambda>a. (a+b)^n" and x=a])
apply (subst binomial_ring)
apply (rule derivative_eq_intros sum.cong | simp add: atMost_atLeast0)+
@@ -30,8 +30,8 @@
lemma binomial_deriv2:
"(\<Sum>k\<le>n. (of_nat k * of_nat (k-1) * of_nat (n choose k)) * a^(k-2) * b^(n-k)) =
- of_nat n * of_nat (n-1) * (a+b::real) ^ (n-2)"
- apply (rule DERIV_unique [where f = "\<lambda>a. of_nat n * (a+b::real) ^ (n-1)" and x=a])
+ of_nat n * of_nat (n-1) * (a+b::real)^(n-2)"
+ apply (rule DERIV_unique [where f = "\<lambda>a. of_nat n * (a+b::real)^(n-1)" and x=a])
apply (subst binomial_deriv1 [symmetric])
apply (rule derivative_eq_intros sum.cong | simp add: Num.numeral_2_eq_2)+
done
@@ -45,7 +45,7 @@
lemma sum_kk_Bernstein [simp]: "(\<Sum>k\<le>n. real k * (real k - 1) * Bernstein n k x) = real n * (real n - 1) * x\<^sup>2"
proof -
have "(\<Sum>k\<le>n. real k * (real k - 1) * Bernstein n k x) =
- (\<Sum>k\<le>n. real k * real (k - Suc 0) * real (n choose k) * x ^ (k - 2) * (1 - x) ^ (n - k) * x\<^sup>2)"
+ (\<Sum>k\<le>n. real k * real (k - Suc 0) * real (n choose k) * x^(k - 2) * (1 - x)^(n - k) * x\<^sup>2)"
proof (rule sum.cong [OF refl], simp)
fix k
assume "k \<le> n"
@@ -54,7 +54,7 @@
then show "k = 0 \<or>
(real k - 1) * Bernstein n k x =
real (k - Suc 0) *
- (real (n choose k) * (x ^ (k - 2) * ((1 - x) ^ (n - k) * x\<^sup>2)))"
+ (real (n choose k) * (x^(k - 2) * ((1 - x)^(n - k) * x\<^sup>2)))"
by cases (auto simp add: Bernstein_def power2_eq_square algebra_simps)
qed
also have "... = real_of_nat n * real_of_nat (n - Suc 0) * x\<^sup>2"
@@ -189,7 +189,7 @@
lemma diff: "f \<in> R \<Longrightarrow> g \<in> R \<Longrightarrow> (\<lambda>x. f x - g x) \<in> R"
unfolding diff_conv_add_uminus by (metis add minus)
- lemma power: "f \<in> R \<Longrightarrow> (\<lambda>x. f x ^ n) \<in> R"
+ lemma power: "f \<in> R \<Longrightarrow> (\<lambda>x. f x^n) \<in> R"
by (induct n) (auto simp: const mult)
lemma sum: "\<lbrakk>finite I; \<And>i. i \<in> I \<Longrightarrow> f i \<in> R\<rbrakk> \<Longrightarrow> (\<lambda>x. \<Sum>i \<in> I. f i x) \<in> R"
@@ -292,13 +292,11 @@
have p01: "p x \<in> {0..1}" if t: "x \<in> S" for x
proof -
have "0 \<le> p x"
- using subU cardp t
- apply (simp add: p_def field_split_simps sum_nonneg)
- apply (rule sum_nonneg)
- using pf01 by force
+ using subU cardp t pf01
+ by (fastforce simp add: p_def field_split_simps intro: sum_nonneg)
moreover have "p x \<le> 1"
- using subU cardp t
- apply (simp add: p_def field_split_simps sum_nonneg)
+ using subU cardp t
+ apply (simp add: p_def field_split_simps)
apply (rule sum_bounded_above [where 'a=real and K=1, simplified])
using pf01 by force
ultimately show ?thesis
@@ -338,7 +336,7 @@
using \<delta>01 unfolding k_def by linarith
with \<delta>01 k2\<delta> have k\<delta>: "1 < k*\<delta>" "k*\<delta> < 2"
by (auto simp: field_split_simps)
- define q where [abs_def]: "q n t = (1 - p t ^ n) ^ (k^n)" for n t
+ define q where [abs_def]: "q n t = (1 - p t^n)^(k^n)" for n t
have qR: "q n \<in> R" for n
by (simp add: q_def const diff power pR)
have q01: "\<And>n t. t \<in> S \<Longrightarrow> q n t \<in> {0..1}"
@@ -352,10 +350,10 @@
then have "1 - (k * \<delta> / 2)^n \<le> 1 - (k * p t)^n"
using \<open>k>0\<close> p01 t by (simp add: power_mono)
also have "... \<le> q n t"
- using Bernoulli_inequality [of "- ((p t)^n)" "k^n"]
+ using Bernoulli_inequality [of "- ((p t)^n)" "k^n"]
apply (simp add: q_def)
by (metis IntE atLeastAtMost_iff p01 power_le_one power_mult_distrib t)
- finally have "1 - (k * \<delta> / 2) ^ n \<le> q n t" .
+ finally have "1 - (k * \<delta> / 2)^n \<le> q n t" .
} note limitV = this
{ fix t and n::nat
assume t: "t \<in> S - U"
@@ -363,35 +361,30 @@
by (simp add: pt_\<delta>)
with k\<delta> have kpt: "1 < k * p t"
by (blast intro: less_le_trans)
- have ptn_pos: "0 < p t ^ n"
+ have ptn_pos: "0 < p t^n"
using pt_pos [OF t] by simp
- have ptn_le: "p t ^ n \<le> 1"
+ have ptn_le: "p t^n \<le> 1"
by (meson DiffE atLeastAtMost_iff p01 power_le_one t)
- have "q n t = (1/(k^n * (p t)^n)) * (1 - p t ^ n) ^ (k^n) * k^n * (p t)^n"
+ have "q n t = (1/(k^n * (p t)^n)) * (1 - p t^n)^(k^n) * k^n * (p t)^n"
using pt_pos [OF t] \<open>k>0\<close> by (simp add: q_def)
- also have "... \<le> (1/(k * (p t))^n) * (1 - p t ^ n) ^ (k^n) * (1 + k^n * (p t)^n)"
+ also have "... \<le> (1/(k * (p t))^n) * (1 - p t^n)^(k^n) * (1 + k^n * (p t)^n)"
using pt_pos [OF t] \<open>k>0\<close>
- apply simp
- apply (simp flip: times_divide_eq_right)
- apply (rule mult_left_mono [of "1::real", simplified])
- apply (simp_all add: power_mult_distrib ptn_le)
- done
- also have "... \<le> (1/(k * (p t))^n) * (1 - p t ^ n) ^ (k^n) * (1 + (p t)^n) ^ (k^n)"
- apply (rule mult_left_mono [OF Bernoulli_inequality [of "p t ^ n" "k^n"]])
- using \<open>k>0\<close> ptn_pos ptn_le
- apply (auto simp: power_mult_distrib)
- done
- also have "... = (1/(k * (p t))^n) * (1 - p t ^ (2*n)) ^ (k^n)"
+ by (simp add: divide_simps mult_left_mono ptn_le)
+ also have "... \<le> (1/(k * (p t))^n) * (1 - p t^n)^(k^n) * (1 + (p t)^n)^(k^n)"
+ proof (rule mult_left_mono [OF Bernoulli_inequality])
+ show "0 \<le> 1 / (real k * p t)^n * (1 - p t^n)^k^n"
+ using ptn_pos ptn_le by (auto simp: power_mult_distrib)
+ qed (use ptn_pos in auto)
+ also have "... = (1/(k * (p t))^n) * (1 - p t^(2*n))^(k^n)"
using pt_pos [OF t] \<open>k>0\<close>
by (simp add: algebra_simps power_mult power2_eq_square flip: power_mult_distrib)
also have "... \<le> (1/(k * (p t))^n) * 1"
- apply (rule mult_left_mono [OF power_le_one])
- using pt_pos \<open>k>0\<close> p01 power_le_one t apply auto
- done
+ using pt_pos \<open>k>0\<close> p01 power_le_one t
+ by (intro mult_left_mono [OF power_le_one]) auto
also have "... \<le> (1 / (k*\<delta>))^n"
using \<open>k>0\<close> \<delta>01 power_mono pt_\<delta> t
by (fastforce simp: field_simps)
- finally have "q n t \<le> (1 / (real k * \<delta>)) ^ n " .
+ finally have "q n t \<le> (1 / (real k * \<delta>))^n " .
} note limitNonU = this
define NN
where "NN e = 1 + nat \<lceil>max (ln e / ln (real k * \<delta> / 2)) (- ln e / ln (real k * \<delta>))\<rceil>" for e
@@ -400,14 +393,14 @@
unfolding NN_def by linarith+
have NN1: "(k * \<delta> / 2)^NN e < e" if "e>0" for e
proof -
- have "ln ((real k * \<delta> / 2) ^ NN e) < ln e"
- apply (subst ln_realpow)
- using NN k\<delta> that
- by (force simp add: field_simps)+
- then show ?thesis
+ have "ln ((real k * \<delta> / 2)^NN e) = real (NN e) * ln (real k * \<delta> / 2)"
+ by (simp add: \<open>\<delta>>0\<close> \<open>0 < k\<close> ln_realpow)
+ also have "... < ln e"
+ using NN k\<delta> that by (force simp add: field_simps)
+ finally show ?thesis
by (simp add: \<open>\<delta>>0\<close> \<open>0 < k\<close> that)
qed
- have NN0: "(1/(k*\<delta>)) ^ (NN e) < e" if "e>0" for e
+ have NN0: "(1/(k*\<delta>))^(NN e) < e" if "e>0" for e
proof -
have "0 < ln (real k) + ln \<delta>"
using \<delta>01(1) \<open>0 < k\<close> k\<delta>(1) ln_gt_zero ln_mult by fastforce
@@ -521,7 +514,7 @@
assume x: "x \<in> B"
then have "x \<in> S"
using B by auto
- have "1 - e \<le> (1 - e / card subA) ^ card subA"
+ have "1 - e \<le> (1 - e / card subA)^card subA"
using Bernoulli_inequality [of "-e / card subA" "card subA"] e cardp
by (auto simp: field_simps)
also have "... = (\<Prod>w \<in> subA. 1 - e / card subA)"
@@ -531,10 +524,7 @@
have "\<And>i. i \<in> subA \<Longrightarrow> e / real (card subA) \<le> 1 \<and> 1 - e / real (card subA) < ff i x"
using e \<open>B \<subseteq> S\<close> ff subA(1) x by (force simp: field_split_simps)
then show ?thesis
- apply (simp add: pff_def)
- apply (rule prod_mono_strict [where f = "\<lambda>x. 1 - e / card subA", simplified])
- apply (simp_all add: subA(2))
- done
+ using prod_mono_strict [where f = "\<lambda>x. 1 - e / card subA"] subA(2) by (force simp add: pff_def)
qed
finally have "1 - e < pff x" .
}
@@ -552,13 +542,18 @@
using assms
by (force simp flip: ex_in_conv intro!: two_special)
next
- case False with e show ?thesis
- apply simp
- apply (erule disjE)
- apply (rule_tac [2] x="\<lambda>x. 0" in bexI)
- apply (rule_tac x="\<lambda>x. 1" in bexI)
- apply (auto simp: const)
- done
+ case False
+ then consider "A={}" | "B={}" by force
+ then show ?thesis
+ proof cases
+ case 1
+ with e show ?thesis
+ by (rule_tac x="\<lambda>x. 1" in bexI) (auto simp: const)
+ next
+ case 2
+ with e show ?thesis
+ by (rule_tac x="\<lambda>x. 0" in bexI) (auto simp: const)
+ qed
qed
text\<open>The special case where \<^term>\<open>f\<close> is non-negative and \<^term>\<open>e<1/3\<close>\<close>
@@ -570,30 +565,26 @@
define n where "n = 1 + nat \<lceil>normf f / e\<rceil>"
define A where "A j = {x \<in> S. f x \<le> (j - 1/3)*e}" for j :: nat
define B where "B j = {x \<in> S. f x \<ge> (j + 1/3)*e}" for j :: nat
- have ngt: "(n-1) * e \<ge> normf f" "n\<ge>1"
- using e
- apply (simp_all add: n_def field_simps)
- by (metis real_nat_ceiling_ge mult.commute not_less pos_less_divide_eq)
- then have ge_fx: "(n-1) * e \<ge> f x" if "x \<in> S" for x
+ have ngt: "(n-1) * e \<ge> normf f"
+ using e pos_divide_le_eq real_nat_ceiling_ge[of "normf f / e"]
+ by (fastforce simp add: divide_simps n_def)
+ moreover have "n\<ge>1"
+ by (simp_all add: n_def)
+ ultimately have ge_fx: "(n-1) * e \<ge> f x" if "x \<in> S" for x
using f normf_upper that by fastforce
+ have "closed S"
+ by (simp add: compact compact_imp_closed)
{ fix j
- have A: "closed (A j)" "A j \<subseteq> S"
- apply (simp_all add: A_def Collect_restrict)
- apply (rule continuous_on_closed_Collect_le [OF f continuous_on_const])
- apply (simp add: compact compact_imp_closed)
- done
- have B: "closed (B j)" "B j \<subseteq> S"
- apply (simp_all add: B_def Collect_restrict)
- apply (rule continuous_on_closed_Collect_le [OF continuous_on_const f])
- apply (simp add: compact compact_imp_closed)
- done
- have disj: "(A j) \<inter> (B j) = {}"
+ have "closed (A j)" "A j \<subseteq> S"
+ using \<open>closed S\<close> continuous_on_closed_Collect_le [OF f continuous_on_const]
+ by (simp_all add: A_def Collect_restrict)
+ moreover have "closed (B j)" "B j \<subseteq> S"
+ using \<open>closed S\<close> continuous_on_closed_Collect_le [OF continuous_on_const f]
+ by (simp_all add: B_def Collect_restrict)
+ moreover have "(A j) \<inter> (B j) = {}"
using e by (auto simp: A_def B_def field_simps)
- have "\<exists>f \<in> R. f ` S \<subseteq> {0..1} \<and> (\<forall>x \<in> A j. f x < e/n) \<and> (\<forall>x \<in> B j. f x > 1 - e/n)"
- apply (rule two)
- using e A B disj ngt
- apply simp_all
- done
+ ultimately have "\<exists>f \<in> R. f ` S \<subseteq> {0..1} \<and> (\<forall>x \<in> A j. f x < e/n) \<and> (\<forall>x \<in> B j. f x > 1 - e/n)"
+ using e \<open>1 \<le> n\<close> by (auto intro: two)
}
then obtain xf where xfR: "\<And>j. xf j \<in> R" and xf01: "\<And>j. xf j ` S \<subseteq> {0..1}"
and xfA: "\<And>x j. x \<in> A j \<Longrightarrow> xf j x < e/n"
@@ -607,11 +598,9 @@
have A0: "A 0 = {}"
using fpos e by (fastforce simp: A_def)
have An: "A n = S"
- using e ngt f normf_upper by (fastforce simp: A_def field_simps of_nat_diff)
+ using e ngt \<open>n\<ge>1\<close> f normf_upper by (fastforce simp: A_def field_simps of_nat_diff)
have Asub: "A j \<subseteq> A i" if "i\<ge>j" for i j
- using e that apply (clarsimp simp: A_def)
- apply (erule order_trans, simp)
- done
+ using e that by (force simp: A_def intro: order_trans)
{ fix t
assume t: "t \<in> S"
define j where "j = (LEAST j. t \<in> A j)"
@@ -624,46 +613,31 @@
then have fj1: "f t \<le> (j - 1/3)*e"
by (simp add: A_def)
then have Anj: "t \<notin> A i" if "i<j" for i
- using Aj \<open>i<j\<close>
- apply (simp add: j_def)
- using not_less_Least by blast
+ using Aj \<open>i<j\<close> not_less_Least by (fastforce simp add: j_def)
have j1: "1 \<le> j"
using A0 Aj j_def not_less_eq_eq by (fastforce simp add: j_def)
then have Anj: "t \<notin> A (j-1)"
using Least_le by (fastforce simp add: j_def)
then have fj2: "(j - 4/3)*e < f t"
using j1 t by (simp add: A_def of_nat_diff)
- have ***: "xf i t \<le> e/n" if "i\<ge>j" for i
- using xfA [OF Ai] that by (simp add: less_eq_real_def)
- { fix i
- assume "i+2 \<le> j"
- then obtain d where "i+2+d = j"
- using le_Suc_ex that by blast
- then have "t \<in> B i"
- using Anj e ge_fx [OF t] \<open>1 \<le> n\<close> fpos [OF t] t
- apply (simp add: A_def B_def)
- apply (clarsimp simp add: field_simps of_nat_diff not_le)
- apply (rule order_trans [of _ "e * 2 + (e * (real d * 3) + e * (real i * 3))"])
- apply auto
- done
- then have "xf i t > 1 - e/n"
- by (rule xfB)
- } note **** = this
have xf_le1: "\<And>i. xf i t \<le> 1"
using xf01 t by force
- have "g t = e * (\<Sum>i<j. xf i t) + e * (\<Sum>i=j..n. xf i t)"
- using j1 jn e
- apply (simp add: g_def flip: distrib_left)
- apply (subst sum.union_disjoint [symmetric])
- apply (auto simp: ivl_disj_un)
- done
+ have "g t = e * (\<Sum>i\<le>n. xf i t)"
+ by (simp add: g_def flip: distrib_left)
+ also have "... = e * (\<Sum>i \<in> {..<j} \<union> {j..n}. xf i t)"
+ by (simp add: ivl_disj_un_one(4) jn)
+ also have "... = e * (\<Sum>i<j. xf i t) + e * (\<Sum>i=j..n. xf i t)"
+ by (simp add: distrib_left ivl_disj_int sum.union_disjoint)
also have "... \<le> e*j + e * ((Suc n - j)*e/n)"
- apply (rule add_mono)
- apply (simp_all only: mult_le_cancel_left_pos e)
- apply (rule sum_bounded_above [OF xf_le1, where A = "lessThan j", simplified])
- using sum_bounded_above [of "{j..n}" "\<lambda>i. xf i t", OF ***]
- apply simp
- done
+ proof (intro add_mono mult_left_mono)
+ show "(\<Sum>i<j. xf i t) \<le> j"
+ by (rule sum_bounded_above [OF xf_le1, where A = "lessThan j", simplified])
+ have "xf i t \<le> e/n" if "i\<ge>j" for i
+ using xfA [OF Ai] that by (simp add: less_eq_real_def)
+ then show "(\<Sum>i = j..n. xf i t) \<le> real (Suc n - j) * e / real n"
+ using sum_bounded_above [of "{j..n}" "\<lambda>i. xf i t"]
+ by fastforce
+ qed (use e in auto)
also have "... \<le> j*e + e*(n - j + 1)*e/n "
using \<open>1 \<le> n\<close> e by (simp add: field_simps del: of_nat_Suc)
also have "... \<le> j*e + e*e"
@@ -685,18 +659,26 @@
also have "... = e * (j-1) * (1 - e/n)"
by (simp add: power2_eq_square field_simps)
also have "... \<le> e * (\<Sum>i\<le>j-2. xf i t)"
- using e
- apply simp
- apply (rule order_trans [OF _ sum_bounded_below [OF less_imp_le [OF ****]]])
- using True
- apply (simp_all add: of_nat_diff)
- done
+ proof -
+ { fix i
+ assume "i+2 \<le> j"
+ then obtain d where "i+2+d = j"
+ using le_Suc_ex that by blast
+ then have "t \<in> B i"
+ using Anj e ge_fx [OF t] \<open>1 \<le> n\<close> fpos [OF t] t
+ unfolding A_def B_def
+ by (auto simp add: field_simps of_nat_diff not_le intro: order_trans [of _ "e * 2 + e * d * 3 + e * i * 3"])
+ then have "xf i t > 1 - e/n"
+ by (rule xfB)
+ }
+ moreover have "real (j - Suc 0) * (1 - e / real n) \<le> real (card {..j - 2}) * (1 - e / real n)"
+ using Suc_diff_le True by fastforce
+ ultimately show ?thesis
+ using e True by (auto intro: order_trans [OF _ sum_bounded_below [OF less_imp_le]])
+ qed
also have "... \<le> g t"
- using jn e
- using e xf01 t
- apply (simp add: g_def zero_le_mult_iff image_subset_iff sum_nonneg)
- apply (rule Groups_Big.sum_mono2, auto)
- done
+ using jn e xf01 t
+ by (auto intro!: Groups_Big.sum_mono2 simp add: g_def zero_le_mult_iff image_subset_iff sum_nonneg)
finally show ?thesis .
qed
have "\<bar>f t - g t\<bar> < 2 * e"
@@ -712,17 +694,16 @@
shows "\<exists>g \<in> R. \<forall>x\<in>S. \<bar>f x - g x\<bar> < e"
proof -
have "\<exists>g \<in> R. \<forall>x\<in>S. \<bar>(f x + normf f) - g x\<bar> < 2 * min (e/2) (1/4)"
- apply (rule Stone_Weierstrass_special)
- apply (rule Limits.continuous_on_add [OF f Topological_Spaces.continuous_on_const])
- using normf_upper [OF f] apply force
- apply (simp add: e, linarith)
- done
+ proof (rule Stone_Weierstrass_special)
+ show "continuous_on S (\<lambda>x. f x + normf f)"
+ by (force intro: Limits.continuous_on_add [OF f Topological_Spaces.continuous_on_const])
+ show "\<And>x. x \<in> S \<Longrightarrow> 0 \<le> f x + normf f"
+ using normf_upper [OF f] by force
+ qed (use e in auto)
then obtain g where "g \<in> R" "\<forall>x\<in>S. \<bar>g x - (f x + normf f)\<bar> < e"
by force
then show ?thesis
- apply (rule_tac x="\<lambda>x. g x - normf f" in bexI)
- apply (auto simp: algebra_simps intro: diff const)
- done
+ by (rule_tac x="\<lambda>x. g x - normf f" in bexI) (auto simp: algebra_simps intro: diff const)
qed
@@ -730,31 +711,32 @@
assumes f: "continuous_on S f"
shows "\<exists>F\<in>UNIV \<rightarrow> R. LIM n sequentially. F n :> uniformly_on S f"
proof -
- { fix e::real
- assume e: "0 < e"
- then obtain N::nat where N: "0 < N" "0 < inverse N" "inverse N < e"
- by (auto simp: real_arch_inverse [of e])
- { fix n :: nat and x :: 'a and g :: "'a \<Rightarrow> real"
- assume n: "N \<le> n" "\<forall>x\<in>S. \<bar>f x - g x\<bar> < 1 / (1 + real n)"
- assume x: "x \<in> S"
- have "\<not> real (Suc n) < inverse e"
- using \<open>N \<le> n\<close> N using less_imp_inverse_less by force
- then have "1 / (1 + real n) \<le> e"
- using e by (simp add: field_simps)
- then have "\<bar>f x - g x\<bar> < e"
- using n(2) x by auto
- } note * = this
- have "\<forall>\<^sub>F n in sequentially. \<forall>x\<in>S. \<bar>f x - (SOME g. g \<in> R \<and> (\<forall>x\<in>S. \<bar>f x - g x\<bar> < 1 / (1 + real n))) x\<bar> < e"
- apply (rule eventually_sequentiallyI [of N])
- apply (auto intro: someI2_bex [OF Stone_Weierstrass_basic [OF f]] *)
- done
- } then
+ define h where "h \<equiv> \<lambda>n::nat. SOME g. g \<in> R \<and> (\<forall>x\<in>S. \<bar>f x - g x\<bar> < 1 / (1 + n))"
show ?thesis
- apply (rule_tac x="\<lambda>n::nat. SOME g. g \<in> R \<and> (\<forall>x\<in>S. \<bar>f x - g x\<bar> < 1 / (1 + n))" in bexI)
- prefer 2 apply (force intro: someI2_bex [OF Stone_Weierstrass_basic [OF f]])
- unfolding uniform_limit_iff
- apply (auto simp: dist_norm abs_minus_commute)
- done
+ proof
+ { fix e::real
+ assume e: "0 < e"
+ then obtain N::nat where N: "0 < N" "0 < inverse N" "inverse N < e"
+ by (auto simp: real_arch_inverse [of e])
+ { fix n :: nat and x :: 'a and g :: "'a \<Rightarrow> real"
+ assume n: "N \<le> n" "\<forall>x\<in>S. \<bar>f x - g x\<bar> < 1 / (1 + real n)"
+ assume x: "x \<in> S"
+ have "\<not> real (Suc n) < inverse e"
+ using \<open>N \<le> n\<close> N using less_imp_inverse_less by force
+ then have "1 / (1 + real n) \<le> e"
+ using e by (simp add: field_simps)
+ then have "\<bar>f x - g x\<bar> < e"
+ using n(2) x by auto
+ }
+ then have "\<forall>\<^sub>F n in sequentially. \<forall>x\<in>S. \<bar>f x - h n x\<bar> < e"
+ unfolding h_def
+ by (force intro: someI2_bex [OF Stone_Weierstrass_basic [OF f]] eventually_sequentiallyI [of N])
+ }
+ then show "uniform_limit S h f sequentially"
+ unfolding uniform_limit_iff by (auto simp: dist_norm abs_minus_commute)
+ show "h \<in> UNIV \<rightarrow> R"
+ unfolding h_def by (force intro: someI2_bex [OF Stone_Weierstrass_basic [OF f]])
+ qed
qed
text\<open>A HOL Light formulation\<close>
@@ -769,9 +751,7 @@
shows "\<exists>g. P(g) \<and> (\<forall>x \<in> S. \<bar>f x - g x\<bar> < e)"
proof -
interpret PR: function_ring_on "Collect P"
- apply unfold_locales
- using assms
- by auto
+ by unfold_locales (use assms in auto)
show ?thesis
using PR.Stone_Weierstrass_basic [OF \<open>continuous_on S f\<close> \<open>0 < e\<close>]
by blast
@@ -832,13 +812,17 @@
lemma polynomial_function_mult [intro]:
assumes f: "polynomial_function f" and g: "polynomial_function g"
- shows "polynomial_function (\<lambda>x. f x *\<^sub>R g x)"
- using g
- apply (auto simp: polynomial_function_def bounded_linear_def Real_Vector_Spaces.linear.scaleR const real_polynomial_function.mult o_def)
- apply (rule mult)
- using f
- apply (auto simp: real_polynomial_function_eq)
- done
+ shows "polynomial_function (\<lambda>x. f x *\<^sub>R g x)"
+proof -
+ have "real_polynomial_function (\<lambda>x. h (g x))" if "bounded_linear h" for h
+ using g that unfolding polynomial_function_def o_def bounded_linear_def
+ by (auto simp: real_polynomial_function_eq)
+ moreover have "real_polynomial_function f"
+ by (simp add: f real_polynomial_function_eq)
+ ultimately show ?thesis
+ unfolding polynomial_function_def bounded_linear_def o_def
+ by (auto simp: linear.scaleR)
+qed
lemma polynomial_function_cmul [intro]:
assumes f: "polynomial_function f"
@@ -875,17 +859,26 @@
by (simp add: real_polynomial_function_eq)
lemma real_polynomial_function_power [intro]:
- "real_polynomial_function f \<Longrightarrow> real_polynomial_function (\<lambda>x. f x ^ n)"
+ "real_polynomial_function f \<Longrightarrow> real_polynomial_function (\<lambda>x. f x^n)"
by (induct n) (simp_all add: const mult)
lemma real_polynomial_function_compose [intro]:
assumes f: "polynomial_function f" and g: "real_polynomial_function g"
shows "real_polynomial_function (g o f)"
using g
- apply (induction g rule: real_polynomial_function.induct)
- using f
- apply (simp_all add: polynomial_function_def o_def const add mult)
- done
+proof (induction g rule: real_polynomial_function.induct)
+ case (linear f)
+ then show ?case
+ using f polynomial_function_def by blast
+next
+ case (add f g)
+ then show ?case
+ using f add by (auto simp: polynomial_function_def)
+next
+ case (mult f g)
+ then show ?case
+ using f mult by (auto simp: polynomial_function_def)
+qed auto
lemma polynomial_function_compose [intro]:
assumes f: "polynomial_function f" and g: "polynomial_function g"
@@ -908,55 +901,55 @@
lemma real_polynomial_function_imp_sum:
assumes "real_polynomial_function f"
- shows "\<exists>a n::nat. f = (\<lambda>x. \<Sum>i\<le>n. a i * x ^ i)"
+ shows "\<exists>a n::nat. f = (\<lambda>x. \<Sum>i\<le>n. a i * x^i)"
using assms
proof (induct f)
case (linear f)
- then show ?case
- apply (clarsimp simp add: real_bounded_linear)
- apply (rule_tac x="\<lambda>i. if i=0 then 0 else c" in exI)
- apply (rule_tac x=1 in exI)
- apply (simp add: mult_ac)
- done
+ then obtain c where f: "f = (\<lambda>x. x * c)"
+ by (auto simp add: real_bounded_linear)
+ have "x * c = (\<Sum>i\<le>1. (if i = 0 then 0 else c) * x^i)" for x
+ by (simp add: mult_ac)
+ with f show ?case
+ by fastforce
next
case (const c)
- show ?case
- apply (rule_tac x="\<lambda>i. c" in exI)
- apply (rule_tac x=0 in exI)
- apply (auto simp: mult_ac)
- done
- case (add f1 f2)
- then obtain a1 n1 a2 n2 where
- "f1 = (\<lambda>x. \<Sum>i\<le>n1. a1 i * x ^ i)" "f2 = (\<lambda>x. \<Sum>i\<le>n2. a2 i * x ^ i)"
+ have "c = (\<Sum>i\<le>0. c * x^i)" for x
by auto
then show ?case
- apply (rule_tac x="\<lambda>i. (if i \<le> n1 then a1 i else 0) + (if i \<le> n2 then a2 i else 0)" in exI)
- apply (rule_tac x="max n1 n2" in exI)
+ by fastforce
+ case (add f1 f2)
+ then obtain a1 n1 a2 n2 where
+ "f1 = (\<lambda>x. \<Sum>i\<le>n1. a1 i * x^i)" "f2 = (\<lambda>x. \<Sum>i\<le>n2. a2 i * x^i)"
+ by auto
+ then have "f1 x + f2 x = (\<Sum>i\<le>max n1 n2. ((if i \<le> n1 then a1 i else 0) + (if i \<le> n2 then a2 i else 0)) * x^i)"
+ for x
using sum_max_0 [where m=n1 and n=n2] sum_max_0 [where m=n2 and n=n1]
- apply (simp add: sum.distrib algebra_simps max.commute)
- done
+ by (simp add: sum.distrib algebra_simps max.commute)
+ then show ?case
+ by force
case (mult f1 f2)
then obtain a1 n1 a2 n2 where
- "f1 = (\<lambda>x. \<Sum>i\<le>n1. a1 i * x ^ i)" "f2 = (\<lambda>x. \<Sum>i\<le>n2. a2 i * x ^ i)"
+ "f1 = (\<lambda>x. \<Sum>i\<le>n1. a1 i * x^i)" "f2 = (\<lambda>x. \<Sum>i\<le>n2. a2 i * x^i)"
by auto
then obtain b1 b2 where
- "f1 = (\<lambda>x. \<Sum>i\<le>n1. b1 i * x ^ i)" "f2 = (\<lambda>x. \<Sum>i\<le>n2. b2 i * x ^ i)"
+ "f1 = (\<lambda>x. \<Sum>i\<le>n1. b1 i * x^i)" "f2 = (\<lambda>x. \<Sum>i\<le>n2. b2 i * x^i)"
"b1 = (\<lambda>i. if i\<le>n1 then a1 i else 0)" "b2 = (\<lambda>i. if i\<le>n2 then a2 i else 0)"
by auto
+ then have "f1 x * f2 x = (\<Sum>i\<le>n1 + n2. (\<Sum>k\<le>i. b1 k * b2 (i - k)) * x ^ i)" for x
+ using polynomial_product [of n1 b1 n2 b2] by (simp add: Set_Interval.atLeast0AtMost)
then show ?case
- apply (rule_tac x="\<lambda>i. \<Sum>k\<le>i. b1 k * b2 (i - k)" in exI)
- apply (rule_tac x="n1+n2" in exI)
- using polynomial_product [of n1 b1 n2 b2]
- apply (simp add: Set_Interval.atLeast0AtMost)
- done
+ by force
qed
lemma real_polynomial_function_iff_sum:
- "real_polynomial_function f \<longleftrightarrow> (\<exists>a n::nat. f = (\<lambda>x. \<Sum>i\<le>n. a i * x ^ i))"
- apply (rule iffI)
- apply (erule real_polynomial_function_imp_sum)
- apply (auto simp: linear mult const real_polynomial_function_power real_polynomial_function_sum)
- done
+ "real_polynomial_function f \<longleftrightarrow> (\<exists>a n. f = (\<lambda>x. \<Sum>i\<le>n. a i * x^i))" (is "?lhs = ?rhs")
+proof
+ assume ?lhs then show ?rhs
+ by (metis real_polynomial_function_imp_sum)
+next
+ assume ?rhs then show ?lhs
+ by (auto simp: linear mult const real_polynomial_function_power real_polynomial_function_sum)
+qed
lemma polynomial_function_iff_Basis_inner:
fixes f :: "'a::real_normed_vector \<Rightarrow> 'b::euclidean_space"
@@ -971,10 +964,9 @@
fix h :: "'b \<Rightarrow> real"
assume rp: "\<forall>b\<in>Basis. real_polynomial_function (\<lambda>x. f x \<bullet> b)" and h: "bounded_linear h"
have "real_polynomial_function (h \<circ> (\<lambda>x. \<Sum>b\<in>Basis. (f x \<bullet> b) *\<^sub>R b))"
- apply (rule real_polynomial_function_compose [OF _ linear [OF h]])
using rp
- apply (auto simp: real_polynomial_function_eq polynomial_function_mult)
- done
+ by (force simp: real_polynomial_function_eq polynomial_function_mult
+ intro!: real_polynomial_function_compose [OF _ linear [OF h]])
then show "real_polynomial_function (h \<circ> f)"
by (simp add: euclidean_representation_sum_fun)
qed
@@ -993,10 +985,11 @@
fixes f :: "'a::real_normed_vector \<Rightarrow> 'b::euclidean_space"
assumes "polynomial_function f"
shows "continuous (at x) f"
- apply (rule euclidean_isCont)
- using assms apply (simp add: polynomial_function_iff_Basis_inner)
- apply (force dest: continuous_real_polymonial_function intro: isCont_scaleR)
- done
+proof (rule euclidean_isCont)
+ show "\<And>b. b \<in> Basis \<Longrightarrow> isCont (\<lambda>x. (f x \<bullet> b) *\<^sub>R b) x"
+ using assms continuous_real_polymonial_function
+ by (force simp: polynomial_function_iff_Basis_inner intro: isCont_scaleR)
+qed
lemma continuous_on_polymonial_function:
fixes f :: "'a::real_normed_vector \<Rightarrow> 'b::euclidean_space"
@@ -1024,9 +1017,7 @@
"real_polynomial_function p2" "\<And>x. (f2 has_real_derivative p2 x) (at x)"
by auto
then show ?case
- apply (rule_tac x="\<lambda>x. p1 x + p2 x" in exI)
- apply (auto intro!: derivative_eq_intros)
- done
+ by (rule_tac x="\<lambda>x. p1 x + p2 x" in exI) (auto intro!: derivative_eq_intros)
case (mult f1 f2)
then obtain p1 p2 where
"real_polynomial_function p1" "\<And>x. (f1 has_real_derivative p1 x) (at x)"
@@ -1034,9 +1025,7 @@
by auto
then show ?case
using mult
- apply (rule_tac x="\<lambda>x. f1 x * p2 x + f2 x * p1 x" in exI)
- apply (auto intro!: derivative_eq_intros)
- done
+ by (rule_tac x="\<lambda>x. f1 x * p2 x + f2 x * p1 x" in exI) (auto intro!: derivative_eq_intros)
qed
lemma has_vector_derivative_polynomial_function:
@@ -1048,26 +1037,24 @@
assume "b \<in> Basis"
then
obtain p' where p': "real_polynomial_function p'" and pd: "\<And>x. ((\<lambda>x. p x \<bullet> b) has_real_derivative p' x) (at x)"
- using assms [unfolded polynomial_function_iff_Basis_inner, rule_format] \<open>b \<in> Basis\<close>
- has_real_derivative_polynomial_function
+ using assms [unfolded polynomial_function_iff_Basis_inner] has_real_derivative_polynomial_function
by blast
- have "\<exists>q. polynomial_function q \<and> (\<forall>x. ((\<lambda>u. (p u \<bullet> b) *\<^sub>R b) has_vector_derivative q x) (at x))"
- apply (rule_tac x="\<lambda>x. p' x *\<^sub>R b" in exI)
- using \<open>b \<in> Basis\<close> p'
- apply (simp add: polynomial_function_iff_Basis_inner inner_Basis)
- apply (auto intro: derivative_eq_intros pd)
- done
+ have "polynomial_function (\<lambda>x. p' x *\<^sub>R b)"
+ using \<open>b \<in> Basis\<close> p' const [where 'a=real and c=0]
+ by (simp add: polynomial_function_iff_Basis_inner inner_Basis)
+ then have "\<exists>q. polynomial_function q \<and> (\<forall>x. ((\<lambda>u. (p u \<bullet> b) *\<^sub>R b) has_vector_derivative q x) (at x))"
+ by (fastforce intro: derivative_eq_intros pd)
}
then obtain qf where qf:
"\<And>b. b \<in> Basis \<Longrightarrow> polynomial_function (qf b)"
"\<And>b x. b \<in> Basis \<Longrightarrow> ((\<lambda>u. (p u \<bullet> b) *\<^sub>R b) has_vector_derivative qf b x) (at x)"
by metis
show ?thesis
- apply (rule_tac p'="\<lambda>x. \<Sum>b\<in>Basis. qf b x" in that)
- apply (force intro: qf)
- apply (subst euclidean_representation_sum_fun [of p, symmetric])
- apply (auto intro: has_vector_derivative_sum qf)
- done
+ proof
+ show "\<And>x. (p has_vector_derivative (\<Sum>b\<in>Basis. qf b x)) (at x)"
+ apply (subst euclidean_representation_sum_fun [of p, symmetric])
+ by (auto intro: has_vector_derivative_sum qf)
+ qed (force intro: qf)
qed
lemma real_polynomial_function_separable:
@@ -1075,15 +1062,14 @@
assumes "x \<noteq> y" shows "\<exists>f. real_polynomial_function f \<and> f x \<noteq> f y"
proof -
have "real_polynomial_function (\<lambda>u. \<Sum>b\<in>Basis. (inner (x-u) b)^2)"
- apply (rule real_polynomial_function_sum)
- apply (auto simp: algebra_simps real_polynomial_function_power real_polynomial_function_diff
- const linear bounded_linear_inner_left)
- done
- then show ?thesis
- apply (intro exI conjI, assumption)
- using assms
- apply (force simp add: euclidean_eq_iff [of x y] sum_nonneg_eq_0_iff algebra_simps)
- done
+ proof (rule real_polynomial_function_sum)
+ show "\<And>i. i \<in> Basis \<Longrightarrow> real_polynomial_function (\<lambda>u. ((x - u) \<bullet> i)\<^sup>2)"
+ by (auto simp: algebra_simps real_polynomial_function_diff const linear bounded_linear_inner_left)
+ qed auto
+ moreover have "(\<Sum>b\<in>Basis. ((x - y) \<bullet> b)\<^sup>2) \<noteq> 0"
+ using assms by (force simp add: euclidean_eq_iff [of x y] sum_nonneg_eq_0_iff algebra_simps)
+ ultimately show ?thesis
+ by auto
qed
lemma Stone_Weierstrass_real_polynomial_function:
@@ -1092,13 +1078,11 @@
obtains g where "real_polynomial_function g" "\<And>x. x \<in> S \<Longrightarrow> \<bar>f x - g x\<bar> < e"
proof -
interpret PR: function_ring_on "Collect real_polynomial_function"
- apply unfold_locales
- using assms continuous_on_polymonial_function real_polynomial_function_eq
- apply (auto intro: real_polynomial_function_separable)
- done
+ proof unfold_locales
+ qed (use assms continuous_on_polymonial_function real_polynomial_function_eq
+ in \<open>auto intro: real_polynomial_function_separable\<close>)
show ?thesis
- using PR.Stone_Weierstrass_basic [OF \<open>continuous_on S f\<close> \<open>0 < e\<close>] that
- by blast
+ using PR.Stone_Weierstrass_basic [OF \<open>continuous_on S f\<close> \<open>0 < e\<close>] that by blast
qed
theorem Stone_Weierstrass_polynomial_function:
@@ -1111,40 +1095,35 @@
{ fix b :: 'b
assume "b \<in> Basis"
have "\<exists>p. real_polynomial_function p \<and> (\<forall>x \<in> S. \<bar>f x \<bullet> b - p x\<bar> < e / DIM('b))"
- apply (rule exE [OF Stone_Weierstrass_real_polynomial_function [OF S _, of "\<lambda>x. f x \<bullet> b" "e / card Basis"]])
- using e f
- apply (auto intro: continuous_intros)
- done
+ proof (rule Stone_Weierstrass_real_polynomial_function [OF S _, of "\<lambda>x. f x \<bullet> b" "e / card Basis"])
+ show "continuous_on S (\<lambda>x. f x \<bullet> b)"
+ using f by (auto intro: continuous_intros)
+ qed (use e in auto)
}
then obtain pf where pf:
"\<And>b. b \<in> Basis \<Longrightarrow> real_polynomial_function (pf b) \<and> (\<forall>x \<in> S. \<bar>f x \<bullet> b - pf b x\<bar> < e / DIM('b))"
- apply (rule bchoice [rule_format, THEN exE])
- apply assumption
- apply (force simp add: intro: that)
- done
- have "polynomial_function (\<lambda>x. \<Sum>b\<in>Basis. pf b x *\<^sub>R b)"
- using pf
- by (simp add: polynomial_function_sum polynomial_function_mult real_polynomial_function_eq)
- moreover
+ by metis
+ let ?g = "\<lambda>x. \<Sum>b\<in>Basis. pf b x *\<^sub>R b"
{ fix x
assume "x \<in> S"
have "norm (\<Sum>b\<in>Basis. (f x \<bullet> b) *\<^sub>R b - pf b x *\<^sub>R b) \<le> (\<Sum>b\<in>Basis. norm ((f x \<bullet> b) *\<^sub>R b - pf b x *\<^sub>R b))"
by (rule norm_sum)
also have "... < of_nat DIM('b) * (e / DIM('b))"
- apply (rule sum_bounded_above_strict)
- apply (simp add: Real_Vector_Spaces.scaleR_diff_left [symmetric] pf \<open>x \<in> S\<close>)
- apply (rule DIM_positive)
- done
+ proof (rule sum_bounded_above_strict)
+ show "\<And>i. i \<in> Basis \<Longrightarrow> norm ((f x \<bullet> i) *\<^sub>R i - pf i x *\<^sub>R i) < e / real DIM('b)"
+ by (simp add: Real_Vector_Spaces.scaleR_diff_left [symmetric] pf \<open>x \<in> S\<close>)
+ qed (rule DIM_positive)
also have "... = e"
by (simp add: field_simps)
finally have "norm (\<Sum>b\<in>Basis. (f x \<bullet> b) *\<^sub>R b - pf b x *\<^sub>R b) < e" .
}
- ultimately
- show ?thesis
- apply (subst euclidean_representation_sum_fun [of f, symmetric])
- apply (rule_tac x="\<lambda>x. \<Sum>b\<in>Basis. pf b x *\<^sub>R b" in exI)
- apply (auto simp flip: sum_subtractf)
- done
+ then have "\<forall>x\<in>S. norm ((\<Sum>b\<in>Basis. (f x \<bullet> b) *\<^sub>R b) - ?g x) < e"
+ by (auto simp flip: sum_subtractf)
+ moreover
+ have "polynomial_function ?g"
+ using pf by (simp add: polynomial_function_sum polynomial_function_mult real_polynomial_function_eq)
+ ultimately show ?thesis
+ using euclidean_representation_sum_fun [of f] by (metis (no_types, lifting))
qed
proposition Stone_Weierstrass_uniform_limit:
@@ -1184,35 +1163,42 @@
lemma path_approx_polynomial_function:
fixes g :: "real \<Rightarrow> 'b::euclidean_space"
assumes "path g" "0 < e"
- shows "\<exists>p. polynomial_function p \<and>
- pathstart p = pathstart g \<and>
- pathfinish p = pathfinish g \<and>
- (\<forall>t \<in> {0..1}. norm(p t - g t) < e)"
+ obtains p where "polynomial_function p" "pathstart p = pathstart g" "pathfinish p = pathfinish g"
+ "\<And>t. t \<in> {0..1} \<Longrightarrow> norm(p t - g t) < e"
proof -
obtain q where poq: "polynomial_function q" and noq: "\<And>x. x \<in> {0..1} \<Longrightarrow> norm (g x - q x) < e/4"
using Stone_Weierstrass_polynomial_function [of "{0..1}" g "e/4"] assms
by (auto simp: path_def)
- have pf: "polynomial_function (\<lambda>t. q t + (g 0 - q 0) + t *\<^sub>R (g 1 - q 1 - (g 0 - q 0)))"
- by (force simp add: poq)
- have *: "\<And>t. t \<in> {0..1} \<Longrightarrow> norm (((q t - g t) + (g 0 - q 0)) + (t *\<^sub>R (g 1 - q 1) + t *\<^sub>R (q 0 - g 0))) < (e/4 + e/4) + (e/4+e/4)"
- apply (intro Real_Vector_Spaces.norm_add_less)
- using noq
- apply (auto simp: norm_minus_commute intro: le_less_trans [OF mult_left_le_one_le noq] simp del: less_divide_eq_numeral1)
- done
- show ?thesis
- apply (intro exI conjI)
- apply (rule pf)
- using *
- apply (auto simp add: pathstart_def pathfinish_def algebra_simps)
- done
+ define pf where "pf \<equiv> \<lambda>t. q t + (g 0 - q 0) + t *\<^sub>R (g 1 - q 1 - (g 0 - q 0))"
+ show thesis
+ proof
+ show "polynomial_function pf"
+ by (force simp add: poq pf_def)
+ show "norm (pf t - g t) < e"
+ if "t \<in> {0..1}" for t
+ proof -
+ have *: "norm (((q t - g t) + (g 0 - q 0)) + (t *\<^sub>R (g 1 - q 1) + t *\<^sub>R (q 0 - g 0))) < (e/4 + e/4) + (e/4+e/4)"
+ proof (intro Real_Vector_Spaces.norm_add_less)
+ show "norm (q t - g t) < e / 4"
+ by (metis noq norm_minus_commute that)
+ show "norm (t *\<^sub>R (g 1 - q 1)) < e / 4"
+ using noq that le_less_trans [OF mult_left_le_one_le noq]
+ by auto
+ show "norm (t *\<^sub>R (q 0 - g 0)) < e / 4"
+ using noq that le_less_trans [OF mult_left_le_one_le noq]
+ by simp (metis norm_minus_commute order_refl zero_le_one)
+ qed (use noq norm_minus_commute that in auto)
+ then show ?thesis
+ by (auto simp add: algebra_simps pf_def)
+ qed
+ qed (auto simp add: path_defs pf_def)
qed
proposition connected_open_polynomial_connected:
fixes S :: "'a::euclidean_space set"
assumes S: "open S" "connected S"
and "x \<in> S" "y \<in> S"
- shows "\<exists>g. polynomial_function g \<and> path_image g \<subseteq> S \<and>
- pathstart g = x \<and> pathfinish g = y"
+ obtains g where "polynomial_function g" "path_image g \<subseteq> S" "pathstart g = x" "pathfinish g = y"
proof -
have "path_connected S" using assms
by (simp add: connected_open_path_connected)
@@ -1224,23 +1210,37 @@
by (simp add: gt_ex)
next
case False
- then have "- S \<noteq> {}" by blast
- then show ?thesis
- apply (rule_tac x="setdist (path_image p) (-S)" in exI)
- using S p
- apply (simp add: setdist_gt_0_compact_closed compact_path_image open_closed)
- using setdist_le_dist [of _ "path_image p" _ "-S"]
- by fastforce
+ show ?thesis
+ proof (intro exI conjI ballI)
+ show "\<And>x. x \<in> path_image p \<Longrightarrow> ball x (setdist (path_image p) (-S)) \<subseteq> S"
+ using setdist_le_dist [of _ "path_image p" _ "-S"] by fastforce
+ show "0 < setdist (path_image p) (- S)"
+ using S p False
+ by (fastforce simp add: setdist_gt_0_compact_closed compact_path_image open_closed)
+ qed
qed
then obtain e where "0 < e"and eb: "\<And>x. x \<in> path_image p \<Longrightarrow> ball x e \<subseteq> S"
by auto
- show ?thesis
- using path_approx_polynomial_function [OF \<open>path p\<close> \<open>0 < e\<close>]
- apply clarify
- apply (intro exI conjI, assumption)
- using p
- apply (fastforce simp add: dist_norm path_image_def norm_minus_commute intro: eb [THEN subsetD])+
- done
+ obtain pf where "polynomial_function pf" and pf: "pathstart pf = pathstart p" "pathfinish pf = pathfinish p"
+ and pf_e: "\<And>t. t \<in> {0..1} \<Longrightarrow> norm(pf t - p t) < e"
+ using path_approx_polynomial_function [OF \<open>path p\<close> \<open>0 < e\<close>] by blast
+ show thesis
+ proof
+ show "polynomial_function pf"
+ by fact
+ show "pathstart pf = x" "pathfinish pf = y"
+ by (simp_all add: p pf)
+ show "path_image pf \<subseteq> S"
+ unfolding path_image_def
+ proof clarsimp
+ fix x'::real
+ assume "0 \<le> x'" "x' \<le> 1"
+ then have "dist (p x') (pf x') < e"
+ by (metis atLeastAtMost_iff dist_commute dist_norm pf_e)
+ then show "pf x' \<in> S"
+ by (metis \<open>0 \<le> x'\<close> \<open>x' \<le> 1\<close> atLeastAtMost_iff eb imageI mem_ball path_image_def subset_iff)
+ qed
+ qed
qed
lemma differentiable_componentwise_within:
@@ -1351,8 +1351,7 @@
with cardB have "n = card B" "dim T = n"
by (auto simp: card_image)
have fx: "(\<Sum>i\<in>B. (f x \<bullet> i) *\<^sub>R i) = f x" if "x \<in> S" for x
- apply (rule orthonormal_basis_expand [OF orthB B1 _ \<open>finite B\<close>])
- using \<open>f ` S \<subseteq> T\<close> spanB that by auto
+ by (metis (no_types, lifting) B1 \<open>finite B\<close> assms(5) image_subset_iff orthB orthonormal_basis_expand spanB sum.cong that)
have cont: "continuous_on S (\<lambda>x. \<Sum>i\<in>B. (f x \<bullet> i) *\<^sub>R i)"
by (intro continuous_intros contf)
obtain g where "polynomial_function g"
@@ -1364,9 +1363,7 @@
show ?thesis
proof
show "polynomial_function (\<lambda>x. \<Sum>i\<in>B. (g x \<bullet> i) *\<^sub>R i)"
- apply (rule polynomial_function_sum)
- apply (simp add: \<open>finite B\<close>)
- using \<open>polynomial_function g\<close> by auto
+ using \<open>polynomial_function g\<close> by (force intro: \<open>finite B\<close>)
show "(\<lambda>x. \<Sum>i\<in>B. (g x \<bullet> i) *\<^sub>R i) ` S \<subseteq> T"
using \<open>B \<subseteq> T\<close>
by (blast intro: subspace_sum subspace_mul \<open>subspace T\<close>)
@@ -1374,9 +1371,7 @@
proof -
have orth': "pairwise (\<lambda>i j. orthogonal ((f x \<bullet> i) *\<^sub>R i - (g x \<bullet> i) *\<^sub>R i)
((f x \<bullet> j) *\<^sub>R j - (g x \<bullet> j) *\<^sub>R j)) B"
- apply (rule pairwise_mono [OF orthB])
- apply (auto simp: orthogonal_def inner_diff_right inner_diff_left)
- done
+ by (auto simp: orthogonal_def inner_diff_right inner_diff_left intro: pairwise_mono [OF orthB])
then have "(norm (\<Sum>i\<in>B. (f x \<bullet> i) *\<^sub>R i - (g x \<bullet> i) *\<^sub>R i))\<^sup>2 =
(\<Sum>i\<in>B. (norm ((f x \<bullet> i) *\<^sub>R i - (g x \<bullet> i) *\<^sub>R i))\<^sup>2)"
by (simp add: norm_sum_Pythagorean [OF \<open>finite B\<close> orth'])