cos(π/6-a)=根号3/3 则sin(5π/6-2a)值

问题描述:

cos(π/6-a)=根号3/3 则sin(5π/6-2a)值

sin(5π/6-2a)=sin(π/2+π/3-2a)
=cos(π/3-2a)
=[cos(π/6-a)]^2-[sin(π/6-a)]^2
=1/3-2/3
=-1/3