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

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The integral of xln(x) from 0 to 1 evaluates to -1/4, as confirmed by Wolfram Alpha. The approach involves calculating the integral from a limit ε to 1, resulting in a term that approaches zero as ε approaches 0. The justification for this limit relies on the properties of improper integrals and the behavior of the integrand near the singularity at x = 0. The continuity of the function and its integrability over the specified interval support this conclusion. Understanding these concepts clarifies the evaluation of the integral despite the singularity.
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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.
 
Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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