At a certain point, two waves produce pressure variations given by p1 = pm sin wt and

At a certain point, two waves produce pressure variations given by Δp1 = Δpm sin wt and Δp2 = Δpm sin (wt – Φ). At this point, what is the ratio Δpr/Δpm where Δpr, is the pressure amplitude of the resultant wave, if d is

(a) 0,

(b) π/2,

(c) π/3, and

(d) π/4?