1. The problem statement, all variables and given/known data I'm trying to find what a a left and right identity element is. Also, I want to see if a one sided element for * exists, if it is unique. 2. Relevant equations 3. The attempt at a solution Ok, I just don't really know what a one sided element is. I'm using e*s=s*e=s, but is e*s the left identity? I think my problem with finding uniqueness is getting started and the fact that I don't really understand what a one sided identity element is?