Kinetic Energy of a Pendulum

1. The problem statement, all variables and given/known data

I want to find the equation of the kinetic energy of a pendulum at any point. I know the initial angle it is released from but I am having trouble finding the velocity at any point to be able to find the kinetic energy at any point.







2. Relevant equations



θ = θ_maxcos(w*t) where w = √g/L



I = mL²



KE_rotational=(1/2) *I([itex]\frac{dθ}{dt}[/itex])²













3. The attempt at a solution



I differentiated the θ function with respect to time to get dθ/dt



[itex]\frac{dθ}{dt}[/itex]=-θ_max*w*sin(w*t)



I have plugged that in to find the kinetic energy but thats apparently not the right answer.