1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Integrals of (-3csc(theta))/(1+cos(theta))

  1. Oct 6, 2014 #1
    1. The problem statement, all variables and given/known data
    integrate (-3csc(theta))/(1+cos(theta))

    2. Relevant equations
    i'm not sure

    3. The attempt at a solution
    i tried using u sub. but i got nowhere.

    U=1+costheta
    Du=-sintheta
     
  2. jcsd
  3. Oct 6, 2014 #2
    The reason why your ##u##-sub doesn't get you anywhere (yet) is because (1) there isn't a ##\sin\theta## in the numerator and (2) we'd still need to deal with the ##\csc\theta##. I recommend that you

    (1) Put a ##\sin\theta## in the numerator so that your ##u##-sub at least has a chance of working. Of course you can't just put one there, but you can multiply the integrand by ##\frac{\sin\theta}{\sin\theta}## so that there is one there.

    (2) Write the ##\csc\theta## in terms of ##\sin\theta## and see if you can make something happen with what you end up with.
     
  4. Oct 6, 2014 #3

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    I'd try just u=cos(theta). Then since du=sin(theta)dtheta multiply numerator and denominator by sin(theta). That gives you your du. Now see if you can use trig identities to express the other functions of theta as u.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted