F.4 trigonometry---
回答 (1)
2010-02-25 7:09 am
✔ 最佳答案
sin3x + cos3x = sinx + cosxsin 3x - sin x = cos x - cos 3x
2 sin x cos 2x = 2 sin 2x sin x
sin x (sin 2x - cos 2x) = 0
sin x = 0 or tan 2x = 1
x = 0, π or 2x = π/4, 5π/4
x = 0, π, π/8 or 5π/8
參考: Myself
收錄日期: 2021-04-13 17:06:41
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20100224000051KK01386