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Math Help - half angles ..

  1. #1
    MHF Contributor
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    half angles ..

    show that tan 22.5 = square root 2 -1


    thanks for any help ..
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  2. #2
    MHF Contributor red_dog's Avatar
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    Use the identity \displaystyle\tan\frac{x}{2}=\sqrt{\frac{1-\cos x}{1+\cos x}} for x=45^{\circ}
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