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    Trigonometry Problems and Identities

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    Please see the attachment for the exact notations and questions in their original format. Basically, what I need help with is the following:

    1) Use formulas for lower powers to rewrite the expression in terms of the first power of cosine.
    a) cos (^4)x
    b) (cos (^4)x) (sin (^2)x)
    c) cos (^6)x

    2) Prove the identity
    a) 4 [(sin (^6)x) + (cos (^6)x)] = 4-3(sin (^2)2x)
    b) Show that cos100 - cos200 = sin50
    c) Show that cos87-cos33 = sin63
    d) cot(x+y) = ((cotx)(coty) - 1)/cotx + coty
    e) cos (x+y) cos (x-y) = cos (^2)x - sin (^2)y
    f) tan (x-y) + (tany-z) + tan (z-x) = tan (x-y) (tany-z) (tanz-x)

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    https://brainmass.com/math/trigonometry/trigonometry-problems-identities-508915

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    Solution Summary

    Trigonometry problems and identities are examined.

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