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Math Help - differentiating - please help

  1. #1
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    differentiating - please help

    Ive used the compsite rule to differentiate e^cosx to get -sinx(e^cosx) (hope i got that bit right)

    I now need to use another rule and my answer to diferentiate:

    (1-cosx)e^cosx

    the answer i came up with was:

    (-(-sinx)e^cosx)+((1-cosx)(-sinxe^cosx)) which i think is completely wrong, can anyone point me in the right direction please?
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  2. #2
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    I think I might have worked it out however any comments would be greatly appreciated:


    Using the Composite rule I differentiated e^cosx to get -sinxe^cosx

    I would then use the product rule now to differentiate (1-cosx)e^cosx?

    I know if h(x)=f(x)g(x)

    f(x)=(1-cosx)
    g(x)=e^cosx

    f’(x)=-(-sinx)
    g’(x)=-sinxe^cosx

    So h’(x)=f’(x)g(x)+g’(x)f(x)

    = (sinxe^cosx) + (-sinxe^cosx)(1-cosx)

    = sinxe^cosx - sinxe^cosx + cosxsinxe^cosx

    = cosxsinxe^cosx

    Does this seem the right way of working it?
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  3. #3
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    Quote Originally Posted by turkish1066 View Post
    e^cosx to get -sinx(e^cosx) (hope i got that bit right)
    Right!

    Quote Originally Posted by turkish1066 View Post
    I now need to use another rule and my answer to diferentiate:

    (1-cosx)e^cosx
    First (1-\cos x)e^{\cos x}=e^{\cos x}-e^{\cos x}\cos x

    Now derive (use the product rule)
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