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Homework Help: 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
    trigonometry


    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

    Hootenanny

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    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
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