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Math Help - Integral over a surface

  1. #1
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    Integral over a surface

    I am having problem with an integral. I dont know how to write in mathcode so excuse me for my notation.

    This is in spherical coordinates:
    x = theta
    y = psi
    r = radial component

    the integrand is: (cos(x)/r^2)

    I want to integrate this over a solid angle of an arbitrary surface.

    da is a differential area. And in spherical coordiantes should be: da = r^2*sin(x)dxdy

    I know the integral should be 4*pi but I dont get it right. I want to have the antiderivate as (cos(x)^2)/2 from 0 to pi.

    Then I get for the whole integral: 1/2*2pi = pi

    So I am missing a factor 4 here. Can anyone help me show what I've missed?
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  2. #2
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    Isn't the integrand

    [LaTeX ERROR: Convert failed]

    In this case, when you integrate with respect to x, you will get [LaTeX ERROR: Convert failed]

    EDIT: I thought I knew what you meant, but I'm not so sure anymore. You should really give some more description of your problem.
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  3. #3
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    Thats exactly the same thing. If you take x from zero to pi you'll end up with 1/2 exactly as i did so it doesnt help to rewrite it.
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