
Jack S. answered 09/29/20
Tutor for ACT/SAT, Computer Science, Calculus, Physics, and English
The power reducing formulae for sine and cosine:
sin2(x) = (1-cos(2x))/2
cos2(x) = (1+cos(2x))/2
16sin2(x)cos2(x) = 16*((1-cos(2x))/2)*((1+cos(2x))/2)
= 4*(1-cos2(2x))
= 4*sin2(2x)
= 2*(1-cos(4x))