cos^2θ+cosθ=?
系吾系等於cos^3θ?
THANKS:-)
cos^2θ+cosθ=?
2011-11-27 11:45 pm
回答 (2)
2011-11-27 11:57 pm
✔ 最佳答案
cos^2θ +cosθ= cosθ(cosθ +1)
因為加所以唔係
要乘先係 cos^2θ x cosθ = cos^3θ
參考: By me
2011-11-28 6:14 am
RHS=cos^3θ
=cos^2θ×cosθ
=[cos2θ+1]/2×cosθ
=(cos2θcosθ+cosθ)/2
=[(cos3θ+cosθ)/2+cosθ]/2
=cos3θ/4+cosθ/4+cosθ
=cos3θ/4+5cosθ/4
LHS=cos^2θ+cosθ
=(cos2θ+1)/2+cosθ
=cos2θ/2+cosθ+1/2
∴RHS≠LHS
=cos^2θ×cosθ
=[cos2θ+1]/2×cosθ
=(cos2θcosθ+cosθ)/2
=[(cos3θ+cosθ)/2+cosθ]/2
=cos3θ/4+cosθ/4+cosθ
=cos3θ/4+5cosθ/4
LHS=cos^2θ+cosθ
=(cos2θ+1)/2+cosθ
=cos2θ/2+cosθ+1/2
∴RHS≠LHS
收錄日期: 2021-04-16 13:52:02
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20111127000051KK00441