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Homework Help: Solid angle/cone

  1. Dec 21, 2011 #1
    Hi everyone

    I'd like to compute the solide angle defined by a cone whose angle θ is known.
    I tried with the definition but I probably mistook since it lead me to compute an integral worth...0.
    I then tried with a rule of three, but the result I get is clearly wrong too.

    Could you explain me how to proceed?
     
  2. jcsd
  3. Dec 21, 2011 #2
    Try this:
    [itex]\int_0^{2\pi}\,\int_0^\theta\,sin\theta\,\mathrm{d}\theta\,\mathrm{d}\phi[/itex]

    for a cone with apex angle 2theta

    via wikipedia
     
  4. Dec 22, 2011 #3
    Thank you emgram769: In fact that's almost what I tried to do but I took the second integral with -theta instead of 0 (and we should take 0 because phi is integrated over 2Pi)
     
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