Question

Prove that sin θ - sin θ•cos2 θ = sin3 θ. Show all works of the equation.

Answer 1

I used x instead of Ф.

$sinx- (cos x)^{2} *sinx= (sin x)^{3}$

$sinx(1-(cos x)^{2})=(sin x)^{3}$

You use the fundamental formula sin^2x+cos^2x=1

sinx*sin^2x=sin^3x
sin^3x=sin^3x