For a wave travelling with amplitude a and angular velocity ω at time t, the displacement y is given by y=asinωt
For phase difference ϕ, the general equation is y=asin(ωt+ϕ)
Given equations are y1=sin(ωt+3π)
and y2=sinωt
Comparing with standard equation, we have a1=1,a2=1,ϕ=3π=60∘
Therefore, resultant amplitude is a=a12+a22+2a1a2cosϕ a=1+1+2×0.5=3