1. The problem statement, all variables and given/known data A = 20 cm Given the graph, what is the phase constant(in degrees)? (I have already solved for amplitude and frequency) 2. Relevant equations x(t) = A cos (wt + ϕ) 3. The attempt at a solution x(t) = A cos (wt + ϕ) Taking from t = 0, we find: 10 = 20cos(w*0 + ϕ) 10 = 20cos(ϕ) 1/2 = cos(ϕ) cos-1(1/2) = ϕ ϕ = 60 degrees. I tried submitting the answer and it said check signs, so I entered -60 degrees. Why is this answer negative?