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Math Help - Using Identities to solve the expressions

  1. #1
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    Using Identities to solve the expressions

    Problem 1:
    Find an exact value. Use double or half angle identity

    tan (13pi/12)

    My thoughts:
    I know that 13pi/12 is in quadrant three and tangent is positive.

    I was stuck from the beginning. With the 13pi/12, because it wasn't on the unit circle. So i thought maybe if i turn it into degrees, then i didnt know how to really do that. And i tried thinking of ways to split it, but i only knew how to do it with cosine and sine ones.
    Last edited by yeunju; April 3rd 2009 at 12:31 PM.
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  2. #2
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    Quote Originally Posted by yeunju View Post
    Problem 1:
    Find an exact value. Use double or half angle identity

    tan (13pi/12)

    My thoughts:
    I know that 13pi/12 is in quadrant three and tangent is positive.

    I was stuck from the beginning. With the 13pi/12, because it wasn't on the unit circle. So i thought maybe if i turn it into degrees, then i didnt know how to really do that. And i tried thinking of ways to split it, but i only knew how to do it with cosine and sine ones.

    [snip]
    \tan \frac{13 \pi}{12} = \tan \frac{\pi}{12} = \tan \left( \frac{\pi}{3} - \frac{\pi}{4}\right).
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  3. #3
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    Talking

    If you'd like to use a half- or double-angle formula, you might want to consider the relationship between pi/12 and, say, pi/6...
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