1. The problem statement, all variables and given/known data Two identical traveling waves, moving in the same direction, are out of phase by π/5.0 rad. What is the amplitude of the resultant wave in terms of the common amplitude ym of the two combining waves? (Give the answer as the ratio of the total amplitude to the common amplitude.) 2. Relevant equations Let y=ym.sinx be the equation of a wave where x is a variable time dependent. and ym is the maximum amplitude. Let y=ym.sin(x+ π/5.0) be the equation of a second identical wave but out of phase by π/5.0 In trigonometric equations: sin(a)+sin(b)=2sin(0.5(a+b)).cos(0.5(a-b)) 3. The attempt at a solution the resultant equation will be: Y=ymsinx + ym.sin(x+ π/5.0) Y=ym(sinx + sin(x+ π/5.0)) .............but sinx + sin(x+ π/5.0)=2sin(0.5(x+x+π/5.0)).cos(0.5(x-x-π/5.0)) .................=2sin(x+π/10.0).cos(π/10.0) Y=ym(2sin(x+π/10.0).cos(π/10.0)) then Ym=2ym.cos(π/10.0) therefore Ym/ym=2 cos(π/10.0)=1.902 is that correct ? and is that the ratio they want?