sin(30)=0.5
what is the values of sin(15)?
sin(30)=2sin(15)cos(15)=0.5
sin^2(15)+cos^2(15)=1
then sin(15)=?
sin question
2007-12-06 3:35 am
回答 (1)
2007-12-06 8:07 am
✔ 最佳答案
By Double Angle Formula: cos 2x = 1 - 2sin2 xsin2 15
= (1 - cos 30) / 2
= (2 - √3) / 4
So, sin 15
= √ (2 - √3) / 2
(because sin 15 > 0, we take positive square root)
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原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20071205000051KK02715