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Math Help - compound angle formulas

  1. #1
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    compound angle formulas

    i'm not sure how to do this kind of question:

    " angles x and y are located in the first quadrant such that sinx= 3/5 and cos y=5/13.

    a) determine an exact value for cosx
    b) determine an exact value for siny "
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  2. #2
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    Quote Originally Posted by ineedhelp1234 View Post
    i'm not sure how to do this kind of question:

    " angles x and y are located in the first quadrant such that sinx= 3/5 and cos y=5/13.

    a) determine an exact value for cosx
    b) determine an exact value for siny "
    a) \sin X=\frac{y}{r}=\frac{3}{5}

    Use r^2=x^2+y^2 to solve for x.

    \cos X=\frac{x}{r}

    b) \cos Y=\frac{x}{r}=\frac{5}{13}

    Use r^2=x^2+y^2 to solve for y.

    \sin Y=\frac{y}{r}
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