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Math Help - Guysss i need help

  1. #1
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    Guysss i need help

    Verify:
    sin( pie / 2 - x) = cos x
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by ^_^Engineer_Adam^_^
    Verify:
    sin( pie / 2 - x) = cos x
    The summation identity is:

    \sin(A+B)=\sin(A) \cos(B)+\cos(A) \sin(B).

    Put A=\pi/2, and B=-x giving:

    \sin(\pi/2-x)=\sin(\pi/2) \cos(-x)+\cos(\pi/2) \sin(-x),

    but \sin(\pi/2)=1, and \cos(\pi/2)=0, so:

    \sin(\pi/2+x)= \cos(-x).

    However \cos is an even function so \cos(-x)=\cos(x), hence:

    \sin(\pi/2+x)= \cos(x).

    RonL
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