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!

Homework Help: Integral of trigonometric functions

  1. Dec 1, 2009 #1
    1. The problem statement, all variables and given/known data

    How can I integrate this:

    [tex]\int sin (nt) sin (n \pi t) dt [/tex]

    This actually in the Fourier series.
  2. jcsd
  3. Dec 1, 2009 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Use the trig identity:

    [tex] \sin\theta\sin\phi=\frac{\cos{(\theta-\phi)}-\cos{(\theta+\phi)}}{2}[/tex]
  4. Dec 1, 2009 #3
    You can use the following identity:

    [tex]\sin a \sin b=\frac{\cos(a-b)-\cos(a+b)} 2[/tex]
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook