The superposition of two harmonic waves: u1 = B * sin( a1(r) ) u2 = B * sin( a2(r) ) results in a sinusoidal wave of the form: uint = Bint * sin( a3(r) ) Find a3 and Bint I'm not sure what to do. I can't think of any way to get it into that "form". http://scienceworld.wolfram.com/physics/Interference.html (5) on that link gives the form I would expect. I think the "int" subscript is talking about intensity, and I'm not sure but I don't think either u1 or u2 depend on time. Can anyone help?