1. The problem statement, all variables and given/known data I'm writing a small project as part of my degree, and I am stuck on proving one (probably simple!) thing towards the end. I've shown that the pendulum is periodic and has a total period of 4t2. 2. Relevant equations 3. The attempt at a solution I think I need to rewrite the same ODE with starting point t=0 but I'm having a complete mindblank on how to proceed from here. Any help would be greatly appreciated!