a maths...
回答 (1)
2007-12-14 3:19 am
✔ 最佳答案
cosx + cos2x = 0 2(cosx)^2-1+cosx=0
(2cosx-1)(cosx+1)=0
cosx=1/2 or cosx=-1
x=2πn±π/3 or x=2πn±π
收錄日期: 2021-04-25 13:04:09
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20071213000051KK02742