1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    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 does cos(-pi/2)=0 and others

  1. Nov 8, 2008 #1
    1. The problem statement, all variables and given/known data
    can someone tell me how cos(-pi/2)=0?
    and also how-sin(-pi/2)=1?

    2. Relevant equations

    3. The attempt at a solution
    ive tried using the two special triangles, but they havent worked and i dont know what else to do
  2. jcsd
  3. Nov 8, 2008 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Notice that cosine is an even function and sine is an odd function.

    Whilst it may be obvious, I will point out that the angles are in radians.
    Last edited: Nov 8, 2008
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook