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Math Help - Prove that 2

  1. #1
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    Prove that 2

    if coty = [sin (z + x)]/[cos(z-x) - cos (z+x)]
    then prove that cotx, coty, cotz, are AP.

    my incomplete of soln-
    just converted cot y = cosy/siny
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  2. #2
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    Try using \displaystyle \sin{(\alpha \pm \beta)} \equiv \sin{(\alpha)}\cos{(\beta)} \pm \cos{(\alpha)}\sin{(\beta)}

    and \displaystyle \cos{(\alpha \pm \beta)} \equiv \cos{(\alpha)}\cos{(\beta)} \mp \sin{(\alpha)}\sin{(\beta)}

    and see if you can simplify.
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  3. #3
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    Quote Originally Posted by Prove It View Post
    Try using \displaystyle \sin{(\alpha \pm \beta)} \equiv \sin{(\alpha)}\cos{(\beta)} \pm \cos{(\alpha)}\sin{(\beta)}

    and \displaystyle \cos{(\alpha \pm \beta)} \equiv \cos{(\alpha)}\cos{(\beta)} \mp \sin{(\alpha)}\sin{(\beta)}

    and see if you can simplify.
    yeah done that but bcoming out of my control to solve it
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