Double angle identity for sine:
[tex]\sin(2x) = 2 \sin(x) \cos(x)[/tex]
[tex]\implies 2 \sin(\theta) - \sin(2\theta) \cos(\theta) = 2 \sin(\theta) - 2 \sin(\theta) \cos^2(\theta)[/tex]
Factorize the left side.
[tex]2 \sin(\theta) - 2 \sin(\theta) \cos^2(\theta) = 2 \sin(\theta) \left(1 - \cos^2(\theta)\right)[/tex]
Pythagorean identity:
[tex]\cos^2(x) + \sin^2(x) = 1[/tex]
[tex]\implies 2 \sin(\theta) \left(1 - \cos^2(\theta)\right) = 2 \sin^3(\theta)[/tex]
so that
[tex]\boxed{2 \sin(\theta) - \sin(2\theta) \cos(\theta) = 2 \sin^3(\theta)}[/tex]
