Jhevon did explain this to me, i think, but i forgot it again.

Let's say we want to find the derivative of $\displaystyle sin^3 (5x^2 - 4x) $

now that becomes $\displaystyle 3(sin(5x^2 - 4x))^2 . cos(5x^2 - 4x) . (10x - 4) $

But if it was just $\displaystyle sin(5x^2 - 4x) $ would it have become:

$\displaystyle cos(5x^2 - 4x) . (10x - 4) $ ?