src/HOL/Integration.thy
changeset 31338 d41a8ba25b67
parent 31336 e17f13cd1280
child 31364 46da73330913
equal deleted inserted replaced
31337:a9ed5fcc5e39 31338:d41a8ba25b67
   270                        \<bar>(f(v) - f(u)) - (f'(x) * (v - u))\<bar> \<le> e * (v - u))"
   270                        \<bar>(f(v) - f(u)) - (f'(x) * (v - u))\<bar> \<le> e * (v - u))"
   271   proof (clarsimp)
   271   proof (clarsimp)
   272     fix x :: real assume "a \<le> x" and "x \<le> b"
   272     fix x :: real assume "a \<le> x" and "x \<le> b"
   273     with f' have "DERIV f x :> f'(x)" by simp
   273     with f' have "DERIV f x :> f'(x)" by simp
   274     then have "\<forall>r>0. \<exists>s>0. \<forall>z. z \<noteq> x \<and> \<bar>z - x\<bar> < s \<longrightarrow> \<bar>(f z - f x) / (z - x) - f' x\<bar> < r"
   274     then have "\<forall>r>0. \<exists>s>0. \<forall>z. z \<noteq> x \<and> \<bar>z - x\<bar> < s \<longrightarrow> \<bar>(f z - f x) / (z - x) - f' x\<bar> < r"
   275       by (simp add: DERIV_iff2 LIM_def)
   275       by (simp add: DERIV_iff2 LIM_eq)
   276     with `0 < e` obtain s
   276     with `0 < e` obtain s
   277     where "\<forall>z. z \<noteq> x \<and> \<bar>z - x\<bar> < s \<longrightarrow> \<bar>(f z - f x) / (z - x) - f' x\<bar> < e/2" and "0 < s"
   277     where "\<forall>z. z \<noteq> x \<and> \<bar>z - x\<bar> < s \<longrightarrow> \<bar>(f z - f x) / (z - x) - f' x\<bar> < e/2" and "0 < s"
   278       by (drule_tac x="e/2" in spec, auto)
   278       by (drule_tac x="e/2" in spec, auto)
   279     then have strad [rule_format]:
   279     then have strad [rule_format]:
   280         "\<forall>z. \<bar>z - x\<bar> < s --> \<bar>f z - f x - f' x * (z - x)\<bar> \<le> e/2 * \<bar>z - x\<bar>"
   280         "\<forall>z. \<bar>z - x\<bar> < s --> \<bar>f z - f x - f' x * (z - x)\<bar> \<le> e/2 * \<bar>z - x\<bar>"