I'd like to plot (to try reproduce) dispersion curves of Lamb waves as in http://en.wikipedia.org/wiki/Lamb_waves
But I can't to separate each lines. I was reduce the dispersion equations as X=ωd/Vs, Y=V/Vs, here Vs/Vl=S=0.5;d=0.001;
ContourPlot[Cot[1/2 Sqrt[X^2 (1-1/Y^2)]] Tan[1/2Sqrt[X^2(S^2-1/Y^2)]] == ((d^2 (-2 + Y^2))/( 2 Sqrt[X^2 (S^2 - 1/Y^2)] Sqrt[X^2 (1 - 1/Y^2)]))
Thanks for all. Please, help me to separate lines.