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Thread: combining powers with trigonometry functions

  1. August 11th 2011, 12:04 PM #1
    celtic1234
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    combining powers with trigonometry functions

    Hi

    A solution to a problem i have is;

    x^4.sinx+4x^3.cosx

    does this simplfy to

    sinx^5 + 12cosx^4

    advice appreciated
    John
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  2. August 11th 2011, 12:17 PM #2
    Chris L T521
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    Re: combining powers with trigonometry functions

    Quote Originally Posted by celtic1234 View Post
    Hi

    A solution to a problem i have is;

    x^4.sinx+4x^3.cosx

    does this simplfy to

    sinx^5 + 12cosx^4

    advice appreciated
    John
    No, because x^4 and \sin x are two completely different functions; thus, it's a no-no to carry the x^4 term inside the sine function. To avoid such confusion, I would write it like x^4\sin(x)+4x^3\cos(x).
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  3. August 11th 2011, 12:24 PM #3
    celtic1234
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    Re: combining powers with trigonometry functions

    thank you
    this site is a god send.
    John
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  4. August 11th 2011, 06:23 PM #4
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    Re: combining powers with trigonometry functions

    You could simplify this by taking out a common factor though.

    \displaystyle x^4\sin{(x)} + 4x^3\cos{(x)} = x^3\left[x\sin{(x)} + 4\cos{(x)}\right]
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