trig identities

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Find the exact value of cos (2theta) given csc theta = 8/3 and 0 < theta < pi/2

  • trig identities -

    cscx = 8/3
    sinx = 3/8
    cosx = sqrt [1 - sin^2x] = (sqrt55)/8
    cos(2x) = 2 cos^2x -1 = 46/64 = 23/32

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