sin(30°—α)=1/4 sin(30°+2α)=?
问题描述：
sin(30°—α)=1/4 sin(30°+2α)=?
答
sin(30°-α)=1/4
sin(30°+2α)
= sin[90°-2(30°-α)]
=cos[2(30°-α)]
= 1- 2[sin(30°-α)]^2
= 1- 1/4
=3/4