Trig

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given that sinx=3/4 and cosy=-5/13 and both x and y are in quadrant II, find the exact value of cos(x-y)

  • Trig -

    cos (x-y) = cos x cos y = sin x sin y
    cos x = -sqrt7 /4
    cos y = -5/13
    sin x = 3/4
    sin y = 12/13
    so

    cos(x-y)=5sqrt7/52 - 9/13

  • Trig -

    sorry typo
    cos x cos y + sin x sin y
    5 sqrt 7/52 + 9/13
    = .9467

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