若sin(兀/3-x)=1/4,则cos(兀/3+2x)等于多少

Question

若sin(兀/3-x)=1/4,则cos(兀/3+2x)等于多少

Answer 1

sin(π/3 -x)=cos(x+π/6)=1/4 cos(π/3 +2x)=2cos(x+π/6)-1=-7/8