Integral of xln(x) with 0 as a limit of integration

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SUMMARY

The integral of \( x \ln(x) \) from 0 to 1 evaluates to \(-\frac{1}{4}\) as confirmed by Wolfram Alpha. The calculation involves taking the limit as \(\epsilon\) approaches 0, where the integral from \(\epsilon\) to 1 is expressed as \(-\frac{1}{4} - \frac{1}{4}\epsilon^2(2\ln{\epsilon}-1)\). This limit is justified by the continuity of the function and the properties of improper integrals, specifically addressing the singularity at the lower limit of integration.

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Homework Statement


Not exactly a homework problem, but I noticed that wolfram alpha gives
\displaystyle{\int_{0}^{1}}x\ln{x}\,dx=-\frac{1}{4}
I was wondering why this is so.

2. Homework Equations & solution attempt
For \epsilon>0
\displaystyle{\int_{\epsilon}^{1}}x\ln{x}\,dx=-\frac{1}{4}-\left(\frac{1}{4}\epsilon^2(2\ln{\epsilon}-1)\right)
Taking \epsilon \to 0 gives the answer provided by wolfram alpha.

My question is what justifies this last step of taking \epsilon \to 0? Continuity?
 
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It's the definition of an indefinite integral with a singularity at one end of the interval of integration.
 
Dick said:
It's the definition of an indefinite integral with a singularity at one end of the interval of integration.
Thank you for your help.
 

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