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Math Help - Finding exact values using the sum and difference identity

  1. #1
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    Finding exact values using the sum and difference identity

    How can I find the exact value of  cos\frac{\pi}{12} using the sum and difference identity?

    I'm guessing I'd have to split the fraction up, into 2 parts, but I'm not sure on how to proceed.

    Help appreciated.
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  2. #2
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    Re: Finding exact values using the sum and difference identity

    \cos \left(\dfrac{\pi}{12}\right) = \cos \left(\dfrac{\pi}{4} - \dfrac{\pi}{6}\right)
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    Re: Finding exact values using the sum and difference identity


    Another way . . .

    \frac{\pi}{12} \;=\;\frac{4\pi}{12} - \frac{3\pi}{12} \;=\;\frac{\pi}{3} - \frac{\pi}{4}

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  4. #4
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    Re: Finding exact values using the sum and difference identity

    you can also use the identity cos^2(x/2) = (1+cosx)/2

    by taking (pie)/12 = [pie/6]/2
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  5. #5
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    Re: Finding exact values using the sum and difference identity

    Quote Originally Posted by waqarhaider View Post
    you can also use the identity cos^2(x/2) = (1+cosx)/2

    by taking (pie)/12 = [pie/6]/2
    this is pi ...



    this is pie ...



    ... hungry?
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