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Math Help - Please help! R formula with cubic equation

  1. #1
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    Please help! R formula with cubic equation

    Express 11cosx + 3sinx in the for R cos(x-y), where R and y are constants. Hence find the maximum and minimum values of (11cosx + 3sinx)^3, and the corresponding values of x where 0<x<360 [degrees].

    [I calculated that R = square root of 130 while y = 15.3 degrees, do correct me if I'm wrong.] Thank you!
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  2. #2
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    Re: Please help! R formula with cubic equation

    You are correct so far.

    So you know that the maximum and minimum values of 11cos x + 3sin x are \pm \sqrt{130}?

    Cube those.
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