Time period, T = 2 s
Amplitude, A = 3 cm
At time, t = 0, the radius vector OP makes an angle π/2 with the positive x-axis, i.e., phase angle ϕ = + (π/2)
Therefore, the equation of simple harmonic motion for the x-projection of OP, at time t, is given by the displacement equation:
At time t = 0, OP makes an angle π with the x-axis, in the anticlockwise direction. Hence, phase angle, Φ = + π
Therefore, the equation of simple harmonic motion for the x-projection of OP, at time t, is given as: