
cos(α-β)=cosαcosβ sinαsinβ

sinα>0,cosα 0两边平方:(sinα cosα)= sinα 2sinαcosα

若ranθ=2,sinθ sinθcosθ=() a -4/3 b5/4 c -3/4 d 6/5

回顾: α sin( α β = sinα cosβ cos sinβ cos( α β
图片内容是:cos2α+sin2α

已知sinα=3/5,求sin(2α π/3)-cos(2α π/6)的值

数学题,请手写出来谢 2cosαcos2α 2sinαsin2α怎么化成 2cos(α-2

数学公式:sin2θ=2sinθ*cosθ

已知tanαπ412且π2α0则2sin2αsin2αcosαπ4

已知向量a=(sinα cosα,√2sinα),b=(cosα-sinα,√2cosα),a∈[0