Two Waves Travel Simultaneously Through the Same Medium

Multiple Choice

Two waves travel simultaneously through the same medium. The first wave is described by y₁(x,t) = (2.00 cm) cos[kx-ωt] and the second wave by y₂(x,t) = (3.00 cm) cos(kx-ωt+δ) . If the resulting wave has an amplitude 4.00 cm, what is a possible value of δ?

A) 0.782 rad
B) 0.250 rad
C) 0.644 rad
D) 0.833 rad
E) 1.32 rad