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Find sin è/2 for sin è = 1/4 and è lies in Quadrant I.

  • trig -

    I am going to use
    cos 2A = 1 - 2sin^2 A
    cos è = 1 - 2sin^2 (è/2)

    so we first have to know cos è
    make a diagram using sin è = 1/4
    then cos è = √15/4

    back in our equation...
    √15/4 = 1 - 2sin^2 (è/2)

    which solves to √[(4-√15)/8]

    (I tested my answer on a calculator)

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