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: Proving identities

  1. Sep 11, 2008 #1
    1. The problem statement, all variables and given/known data
    prove: cos^2(x)= (1+cos2x)/(2)


    2. Relevant equations
    i broke the cos^2(x) down to 1-sin^2(x)???


    3. The attempt at a solution
     
  2. jcsd
  3. Sep 11, 2008 #2

    Defennder

    User Avatar
    Homework Helper

    It's easier to start with the right hand side. Just apply the double angle formula on the right.
     
  4. Sep 11, 2008 #3
    this is what i did:

    = (1+cos2x)/(2)
    = (1+ (2cos^2(x)-1))/(2)
    = 2cos^2 (x)/2
    cos^2(x)=cos^2(x)

    look good?
     
  5. Sep 11, 2008 #4

    Defennder

    User Avatar
    Homework Helper

    Yeah looks ok.
     
  6. Sep 11, 2008 #5
    awsome thanksman
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook