# Homework Help: Taylor series for cos[1/(1-z^2)]

1. Feb 19, 2012

### connor415

Bit stuck on this. I tried writing 1/(1-z^2) as taylor series then Cos z as taylor series, then substituting one into the other but it looked a bit dodgy. Can one simple substitute like this?

2. Feb 19, 2012

### vela

Staff Emeritus
Yes, you can, though it tends to be tedious to work out.