# Clarification on Definition of Green Strain

1. Sep 7, 2011

### EvanZ

Hey, everyone. I'm new here. This is a continuum mechanics question. If it's the wrong forum, please let me know, of course.

The question is pretty simple, but since I haven't been able to find an answer, I'm looking for "crowd help". Green strain $\mathbf{E}$ is usually defined implicitly by the following equation:

$ds^2-dS^2=2\mathbf{dX}\cdot \mathbf{E}\cdot\mathbf{dX}$

For the life of me, I can't explain why the 2 is necessary or where it comes from. I assume there's a good reason, though. Any thoughts are appreciated.