1. The problem statement, all variables and given/known data Given a pendulum with fixed length, at what angle does the pendulum have to be released at in order to not follow the standard formula for frequency? 2. Relevant equations P = 2pi*sqrt(l/g) 3. The attempt at a solution I know that this equation holds for "small" angles (theta < 15 degrees?), but at what angle does this break? And why does it not work only after a specific angle?