src/HOL/Library/Formal_Power_Series.thy
changeset 36309 4da07afb065b
parent 35175 61255c81da01
child 36311 ed3a87a7f977
equal deleted inserted replaced
36308:bbcfeddeafbb 36309:4da07afb065b
   584   obtain k::nat where k: "real k > max 0 (- log y x) + 1" by blast
   584   obtain k::nat where k: "real k > max 0 (- log y x) + 1" by blast
   585   from k have kp: "k > 0" by simp
   585   from k have kp: "k > 0" by simp
   586   from k have "real k > - log y x" by simp
   586   from k have "real k > - log y x" by simp
   587   then have "ln y * real k > - ln x" unfolding log_def
   587   then have "ln y * real k > - ln x" unfolding log_def
   588     using ln_gt_zero_iff[OF yp] y1
   588     using ln_gt_zero_iff[OF yp] y1
   589     by (simp add: minus_divide_left field_simps del:minus_divide_left[symmetric] )
   589     by (simp add: minus_divide_left field_eq_simps del:minus_divide_left[symmetric] )
   590   then have "ln y * real k + ln x > 0" by simp
   590   then have "ln y * real k + ln x > 0" by simp
   591   then have "exp (real k * ln y + ln x) > exp 0"
   591   then have "exp (real k * ln y + ln x) > exp 0"
   592     by (simp add: mult_ac)
   592     by (simp add: mult_ac)
   593   then have "y ^ k * x > 1"
   593   then have "y ^ k * x > 1"
   594     unfolding exp_zero exp_add exp_real_of_nat_mult
   594     unfolding exp_zero exp_add exp_real_of_nat_mult
   595     exp_ln[OF xp] exp_ln[OF yp] by simp
   595     exp_ln[OF xp] exp_ln[OF yp] by simp
   596   then have "x > (1/y)^k" using yp 
   596   then have "x > (1/y)^k" using yp 
   597     by (simp add: field_simps nonzero_power_divide )
   597     by (simp add: field_eq_simps nonzero_power_divide )
   598   then show ?thesis using kp by blast
   598   then show ?thesis using kp by blast
   599 qed
   599 qed
   600 lemma X_nth[simp]: "X$n = (if n = 1 then 1 else 0)" by (simp add: X_def)
   600 lemma X_nth[simp]: "X$n = (if n = 1 then 1 else 0)" by (simp add: X_def)
   601 lemma X_power_nth[simp]: "(X^k) $n = (if n = k then 1 else (0::'a::comm_ring_1))"
   601 lemma X_power_nth[simp]: "(X^k) $n = (if n = k then 1 else (0::'a::comm_ring_1))"
   602   by (simp add: X_power_iff)
   602   by (simp add: X_power_iff)