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Math Help - Proofs involving logs

  1. #1
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    Proofs involving logs

    Can anyone show the following?:

    \intlog(x)dx = xlog(x) - x
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  2. #2
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    Hello, Mathman87!

    Can anyone show the following?:

    . . \int \ln x \,dx \;=\; x\ln x - x + C
    Integrate by parts . . .

    . . \begin{array}{ccccccc}u &=& \ln x && dv &=& dx \\ du &=& \frac{dx}{x} && v &=& x \end{array}


    We have: . x\ln x - \int x\left(\tfrac{dx}{x}\right)  \;\;=\;\;x\ln x - \int dx \;\;=\;\; x\ln x - x + C

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  3. #3
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    thank you! much easier than i thought :-)
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