呢一條數點搵個答案? 可唔可以show steps?
5sin4x = 2sin2x
remark:個4同個2唔係power黎的...
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Trigonometry
2007-09-09 5:41 am
回答 (1)
2007-09-09 5:52 am
✔ 最佳答案
*----sin2x=2sinxcosxso sin4x=2sin2xcos2x
5sin4x = 2sin2x
5(2sin2xcos2x)=2sin2x
10sin2xcos2x=2sin2x
sin2x(5cos2x-1)=0
sin2x=0 or 5cos2x=1
2x=0 or 180 or 360 degree cos2x=1/5
x=0 or 90 or 180degree 2x=78.5 or 281.5degree
x=39.25 or 140.75degree
so x=0 or 39.25 or 90 or 140.75 or 180degree
收錄日期: 2021-04-13 13:23:53
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070908000051KK05087