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Math Help - Trigonometric Problem

  1. #1
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    Trigonometric Problem

    Hi there,
    Can anyone give me help to start off this problem please?

    Triangle PQR Angle PRQ = 3x; Angle PQR = x

    I have to prove that p = 4q cos x cos 2x.

    Thanks
    Cromlix
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  2. #2
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    Quote Originally Posted by cromlix View Post
    Hi there,
    Can anyone give me help to start off this problem please?

    Triangle PQR Angle PRQ = 3x; Angle PQR = x

    I have to prove that p = 4q cos x cos 2x.

    Thanks
    Cromlix
    law of sines ...

    \dfrac{q}{\sin{x}} = \dfrac{p}{\sin(180-4x)}

    q\sin(180-4x) = p\sin{x}

    ... taking it from this point will lead to what you want proved
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