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Math Help - finding the exact value

  1. #1
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    finding the exact value

    sin 5 pal/8 i've tried almost every combination ( 5 pal/8 - pal/6, 4 ,3 ,2 ecc) and i'm still struggling..hope ui guys can help me
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  2. #2
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    Quote Originally Posted by alessandromangione View Post
    sin 5 pal/8 i've tried almost every combination ( 5 pal/8 - pal/6, 4 ,3 ,2 ecc) and i'm still struggling..hope ui guys can help me
    pal? do you mean pi , \pi ?

    note that \frac{5\pi}{8} is one-half of \frac{5\pi}{4}

    use the half-angle identity for sine ...

    \sin\left(\frac{t}{2}\right) = \pm \sqrt{\frac{1-\cos{t}}{2}}
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  3. #3
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    Did you mean  \sin\left(\frac{5\pi}{8}\right) ?

    If so

     \sin\left(\frac{\theta}{2}\right)= \pm\sqrt{\frac{1-\cos(\theta)}{2}}

    Now make \theta = \frac{5\pi}{4}
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