Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Substitutions for some trig integrals?

  1. Nov 24, 2008 #1
    Does anybody know substitutions that can be used for the following integrals:

    \int (a^2 - b^2 \cos\theta)^{-3/2} d\theta
    \int (a^2 - b^2 \cos\theta)^{-3/2} \sin\theta d\theta
    \int (a^2 - b^2 \cos\theta)^{-3/2} \cos\theta d\theta

    I also had a look for these in my table of integrals, but didn't see anything appropriate, but am also a bit rusty, and could just be overlooking the obvious.

    EDIT: oops. fixed sign in square root.
    Last edited: Nov 24, 2008
  2. jcsd
  3. Nov 24, 2008 #2
    Funny, how asking the question is enough to see the answer. I see what to do with the second one now, and it gets me halfway to:

    \int (a^2 - b^2 \cos\theta)^{-3/2} e^{i\theta} d\theta

    which is actually what I was after for the second two. However, it's still not obvious to me what to do with the first nor third integrals.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Substitutions for some trig integrals?
  1. Trig substitutions (Replies: 1)