Question

sin(a-π/6)=3/5,求sin(2a+π/6)

Answer 1

sin(2a+π/6)= sin(2a-π/3 +π/2)= -cos(2a-π/3)
=sin(a-π/6)^2 - cos(a-π/6)^2
= (3/5)^2- (4/5)^2
= 7/25