precalculus

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write each expression as the sine, cosine or tangent of a double angle. then find the exact value of the expression.

a. 2sin 22.5 cos 22.5

b. cos^2 105- sin^2 105

  • precalculus -

    a, use
    sin 45 = cos 45 = 1/sqrt 2

    b, use
    105 = (1/2) 210 which is 180 + 30
    so use
    sin 210 = -1/2
    cos 210 = -sqrt 3/2

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