I have looked through the forum here and several other forces. My task is to derive a formula to determine the angle of release of a simple pendulum. I know the mass, velocity at lowest point and I can therefore determine the height or distance it fell mgh=(mv^2)/2. I am not able to locate the geometric/trig brain cells that will let me use this information to determine the angle athough I do know the adjacent side of the similar but smaller triangle. I do not know the length of the string. Could someone point me in the right direction please?