1. The problem statement, all variables and given/known data Cycloidal Pendulum, with x= RΘ+RsinΘ and y = -RcosΘ I need to find the Lagragian. 2. Relevant equations L = T - V 3. The attempt at a solution I just want to know how do I find the velocity so I can find T, which is 1/2 mv². I thought it would be dx/dΘ but it didn't work. Can anyone explain to me how can I find the velocity?