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Complex Trigonometry Question

  1. Aug 28, 2008 #1
    Suppose y = f(x) * sin (kx), where k = wavenumber.

    If [tex]\int y*dy[/tex] = 3*kx, solve for f(x)
  2. jcsd
  3. Aug 28, 2008 #2


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    Hi redtree! :smile:
    erm … [tex]\int y*dy\ =\ \frac{1}{2}\,y^2[/tex] :confused:

    do you mean [tex]\int_0^x y(z)*dz\ =\ 3\,kx[/tex] ?

    If so, just differentatiate both sides. :smile:
  4. Aug 28, 2008 #3


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    If you really do mean [itex]\int y dy= 3kx[/itex], then (1/2)y2+ C= 3kx so
    [tex]y= f(x)sin(kx)= \sqrt{6kx- 2C}[/tex]
    [tex]f(x)= \frac{\sqrt{6kx- 2C}}{sin(kx)}[/tex]
    where C and be any constant.

    But I suspect tiny-tim is right.
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