# How do you differentiate f(x)=(3x-cos^3x)^2/4 using the chain rule?

Nov 8, 2015

Yes, use the chain rule ...

#### Explanation:

$f ' \left(x\right) = \left(\frac{1}{4}\right) \left(2\right) \left(3 x - {\cos}^{3} x\right) \left(3 - 3 {\cos}^{2} x\right) \left(- \sin x\right)$

You can do some simplification:

$f ' \left(x\right) = \left(- \frac{3}{2}\right) \left(3 x - {\cos}^{3} x\right) \left({\sin}^{3} x\right)$

hope that helped