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Math Help - trigonometry

  1. #1
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    trigonometry

    cos(theta + pi)

    sin(theta-3pi/2)

    cos(2pi/9)cos(pi/18) + sin(2pi/9)sin(pi/18)
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  2. #2
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    Quote Originally Posted by desperate_on_sunday_night View Post
    cos(theta + pi)

    sin(theta-3pi/2)

    cos(2pi/9)cos(pi/18) + sin(2pi/9)sin(pi/18)

    \cos(x \pm y) = \cos{x}\cos{y} \mp \sin{x}\sin{y}

    \sin(x \pm y) = \sin{x}\cos{y} \pm \cos{x}\sin{y}
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