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!

How to prove this identity?

  1. Jan 24, 2005 #1
    :mad: how would u proove this identity

    [tex] \cos^2 \theta= \cos^2 - \sin^2= 2\cos^2\theta-1=1-2\sin^2\theta [/tex] ? The example i was given was [tex] \sin2\theta=2\sin\theta \cos\theta [/tex] this was a little bit easier to understand since there was a left and right side, im not sure how to proove this. How was this formula derived from the sum differnce formula?
  2. jcsd
  3. Jan 24, 2005 #2
    cos(a+b) = cos(a)cos(b)-sin(a)sin(b)
    this is the first step... the rest should be easy
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: How to prove this identity?
  1. How to prove? (Replies: 0)

  2. Proving trigo identity (Replies: 2)

  3. Proving trigo identity (Replies: 9)