# Taylor polynomials

1. Nov 1, 2012

### hahaha158

1. The problem statement, all variables and given/known data

Find the degree 3 Taylor polynomial approximation to the function f(x)=5ln(sec(x)) about x=0.

2. Relevant equations

the taylor polynomial equation

3. The attempt at a solution

Here are my derivatives
f(x)=5ln(secx)
f'(x)=5tanx
f''(x)5sec^2(x)
f'''(x)=10sec^2(x)tanx

Please let me know if any of the above are wrong

When I try to plug in 0 for the x's above I end up with a whole lot of undefined answers because sec0=undefined. How can I get around this?

thanks

2. Nov 1, 2012

### Fightfish

Are you sure that $sec 0 = \frac{1}{cos 0}$ is undefined?

3. Nov 1, 2012

### hahaha158

oops, got sec and csc confused. Thanks