# Math Help - another derivative problem

1. ## another derivative problem

im lost...

2. Why don't you try a little by yourself ?

You may know the derivate of a product.

The derivate of arctan(u(x)) is u'(x)/(1+u²(x))

3. The first thing we have is a product rule. There is also one chain rule. So:

$f'(x) = 6x^3\cdot \frac {1}{1+81x^4}\cdot 18x + 18x^2\arctan {9x^2}$

Then just simplify.

4. ## Product rule and chain rule

$f(x)=6x^3 \tan^{-1}(9x^2)$

$f'(x)=18x^2 \tan^{-1}(9x^2)+6x^3 \cdot \left( \frac{18x}{1+(9x^2)^2} \right)$

Just simplify from here.

Good luck.