1. The problem statement, all variables and given/known data A pendulum's angle is given by (.10 rad)cos(5t + pi) where t is in sec. What is the initial angle? 2. Relevant equations 3. The attempt at a solution Do I plug in t= 0 to get this angle, or is the phase constant this angle? I read that the phase constant specifies initial conditions, but I'm not entirely clear on what it means.