Some weird integral with natural logarithm

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SUMMARY

The integral \(\int\left(\dfrac{\ln x}{x}\right)^2 dx\) requires a substitution method for evaluation. The correct substitution involves letting \(u = \ln x\), which simplifies the integrand to \((u^2) \cdot e^{-u} du\). An incorrect approach was noted where \(dv\) was initially set as \(\ln^2 x dx\), which does not yield a solvable form. The proper differential \(dv\) should be \(\frac{1}{x^2} dx\) for accurate integration.

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mrdoe
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Homework Statement



\displaystyle\int\left(\dfrac{\ln x}{x}\right)^2 dx

2. The attempt at a solution

I tried letting u=\ln^2 x and dv the rest and I also tried dv=\ln^2 x dx and u the rest. It won't work out.
 
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Let u = ln(x), => du = 1/x dx.

Then your integrand is [(u^2) / x]du

Well, x = exp(u), so what you really have is (u^2)exp(-u)du

Does that work? You should be able to handle that one...
 
mrdoe said:

Homework Statement



\displaystyle\int\left(\dfrac{\ln x}{x}\right)^2 dx

2. The attempt at a solution

I tried letting u=\ln^2 x and dv the rest and I also tried dv=\ln^2 x dx and u the rest. It won't work out.

your dv is wrong its dv=\frac{1}{x^2} dx
 

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