微積分----->積分
回答 (2)
2011-05-22 6:17 am
✔ 最佳答案
∫ 1 / (x^2 + 9) dx = ∫ 1 / (x^2 + 3^2) dx
Let x = 3tanθ , dx = 3(secθ)^2 dθ
= (1/9) ∫ 3(secθ)^2/(secθ)^2 dθ
= θ/3 + C
= (1/3)arctan(x/3) + C
2011-05-22 6:48 am
收錄日期: 2021-04-26 19:16:25
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20110521000015KK09649