Question

What's the derivative of `arctan(x/3)`?

Answer 1

`f'(x)=3/(x^2+9)`

Explanation:

`f(x)=arctan(x/3)`

Apply the chain rule:

`f'(x)=1/((x/3)^2+1)xx1/3`

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

This can be simplified to:

`f'(x)=3/(x^2+9)`