# Math Help - Derivative of a trig function

1. ## Derivative of a trig function

Hi,

Im confused on what im doing wrong here to simplify this derivative.

The book comes up with a different answer.

2. ## Re: Derivative of a trig function

When you used the chain rule, you should have multiplied instead of subtracting:

$f'(t)=6(\sec(\pi{t}-1))(\sec(\pi{t}-1)\tan(\pi{t}-1))(\pi)$

$f'(t)=6\pi\sec^2(\pi{t}-1)\tan(\pi{t}-1))$

- Hollywood