# Stat. Mech. by Pathria issue

## Homework Statement

Problem 2.9

Solve the integral:

\int \dddot \int dx_{1}dx_{2}\dddot dx_{N}

where

0 \geq \sum_{i=1}^{N}x_{i} \leq R\]

## The Attempt at a Solution

My issue is not really this problem but the general how-to. Pathria, it seems, does not like explaining the how and the why and instead thinks that a single example in Appendix C suffices. My attempt at a solution includes defining

x_{i} = u_{i}^{2}

in order to get the hypervolume defined on a sphere as the condition becomes

0 \geq \sum_{i=1}^{N}u_{i}^{2} \leq R

this is it however since the general theory is not explained. I have never felt so lost before...if anyone could point me to a good resource(I have yet to find any example or explanation online) or could give me a push in the right direction, it would be appreciated.