Question 29?
回答 (1)
2017-05-30 2:30 pm
✔ 最佳答案
lim x→ 0 [ tan (a+x) - tan (a-x) ] / [ arctan (a+x) - arctan (a-x) ]= lim x→ 0 [ sec² (a+x) + sec² (a-x) ] / { 1/[ 1 + (a+x)² ] + 1/[ 1 + (a-x)² ] } , by the l'Hopital's rule
= 2 * sec² a / [ 2 * 1/( 1 + a² ) ]
= ( 1 + a² ) * sec² a
= ( 1 + a² ) / cos² a
Ans : (2)
收錄日期: 2021-05-02 14:13:36
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20170529155428AAn4d5z