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If tanx=5/12 then what is sinx/2?

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    Make a triangle.
    By Pythagoras
    r^2 = 5^2 + 12^2
    r = 13

    so sinx = 5/13 and cosx = 12/13

    I will assume you meant sin(x/2)

    using cosx = 1 - 2sin^2 (x/2)
    12/13 = 1-2sin^2 (x/2)
    2sin^2 (x/2) = 1/13
    sin^2 (x/2) = 1/26
    sin (x/2) = 1/√26 or √26/26

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