1. The problem statement, all variables and given/known data A mass is hanging on a vertical spring, and oscillates in SHM with an amplitude of 10.0 cm, and period 0.500 s. The graph shows its motion as a function of time. At t = 0, the mass is found at x = -7.50 cm below the equilibrium position. Assuming that x(t) = A cos (ωt + φ), find the value of the initial phase angle, φ. 2. Relevant equations 3. The attempt at a solution How do I get started in finding the initial phase angle, φ?