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    using formula for tan2A in terms of Tan A, find exact form of Tan 22.5

    not thinking along right lines. Have to use tan 45 in the formulae. Seems like have to use Tan 1/2 A, but that's half angle formula, and not the tan 2A which is requested. can someone point me in right direction please. ta
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    Let 2A=45, write \tan 45 = \frac{2\tan A}{1-\tan^2 A}. Can you get this as a quadratic in tan A and then solve it?
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    been looking over what you wrote, but still not seeing it.
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    This is a random solution.

    x= 24.1 cm ( to 1 d.p)
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    Following on from what ad absurdum said really....


    tan2A=2tanA/(1-tan²(A))
    A=22.5...tan2A=1

    so when you multiply across (where x=tanA)

    1-x²=2x
    so x²+2x-1=0
    so (x+1)²=2
    so x=-1±√2
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    i see. thx. was having bit of a mind block that night. So the -1 - rt2 part of the solution is ignored, as it's outside the range of +-1
 
 
 
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Updated: October 11, 2006

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