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!

Trig ratios, double angles

  1. Mar 21, 2009 #1
    1. The problem statement, all variables and given/known data
    Prove that sin(45+x).sin(45-x) = [tex]\frac{1}{2}[/tex]cos2x

    2. Relevant equations
    double angle formulae
    reduction formulae
    special angles

    3. The attempt at a solution


  2. jcsd
  3. Mar 21, 2009 #2


    User Avatar
    Gold Member

    How did you get from:




  4. Mar 21, 2009 #3
    I really don't know. I must of been smoking something(hehehe):rofl:
    But thanks any way for pointing out my error I got it now.

    it should be

    Last edited: Mar 21, 2009
  5. Mar 21, 2009 #4
    Start from here:

    http://http://i623.photobucket.com/albums/tt316/Saxifrage_Russell/PhysicsForumcomMarch21st.png" [Broken]

    Last edited by a moderator: May 4, 2017
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook