# What's the derivative of #f(x) = (1/3) (arctan(3x))^2#?

##### 1 Answer

Jan 31, 2016

#### Explanation:

The first issue is the squared function. Use the chain rule:

#f'(x)=2/3(arctan(3x))^1d/dx(arctan(3x))#

To differentiate the

#f'(x)=2/3arctan(3x)*3/(1+9x^2)#

This simplifies to be

#f'(x)=(2arctan(3x))/(1+9x^2)#