# Homework Help: Sum approximation

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1. Jan 13, 2017

### dravis

So this is actually a physics question, but i have a problem with just the math part of it, as i don't really get how to approximate this sum

Problem 7.1

The question is: how one gets Z_rot=1+3e^(-h^2/IkT) ? Is there some kind of formula for approximation ?

Cheers.

2. Relevant equations

3. The attempt at a solution
I tried to perform operations and to simplify the expression but got to a dead end.