So in my book, it derives the expression for power in a travelling transverse mechanical wave. P= Sqrt[(mu)F].(omega)^2.(A)^2 It reduces this from: P=k^2.omega^2.F.A^2.(sin(kx-omega.t)^2 Where all symbols are the standard ones in dealing with waves. Could someone please go thru how it got from 2 to 1? I can't see the logic. I'm sure its obviously just basic math I am overlooking, but there may be a misprint in the derivation. Cheers!