Math

QuestionEvaluate the integral: (lnx)2xdx\int \frac{(\ln x)^{2}}{x} \, dx

Studdy Solution

STEP 1

Assumptions1. We are given the integral (lnx)xdx\int \frac{(\ln x)^{}}{x} d x . We know the basic rules of integration3. We know the method of integration by parts, which is given by udv=uvvdu\int u dv = uv - \int v du

STEP 2

Let's use the method of integration by parts. We need to identify 'u' and 'dv' in our integral.Let's chooseu=(lnx)2u = (\ln x)^{2}anddv=1xdxdv = \frac{1}{x} dx

STEP 3

Now, we need to find 'du' and 'v'.The derivative of 'u' with respect to 'x' gives 'du': du=2lnx1xdx=2lnxxdxdu =2 \ln x \cdot \frac{1}{x} dx =2 \frac{\ln x}{x} dxThe integral of 'dv' gives 'v': v=dv=1xdx=lnxv = \int dv = \int \frac{1}{x} dx = \ln x

STEP 4

Now, we substitute 'u', 'v', 'du', and 'dv' into the integration by parts formulaudv=uvvdu\int u dv = uv - \int v du

STEP 5

Substitute the values for 'u', 'v', 'du', and 'dv' into the formula(lnx)2xdx=(lnx)2lnxlnx2lnxxdx\int \frac{(\ln x)^{2}}{x} dx = (\ln x)^{2} \cdot \ln x - \int \ln x \cdot2 \frac{\ln x}{x} dx

STEP 6

implify the equation=(lnx)32(lnx)2xdx= (\ln x)^{3} -2 \int \frac{(\ln x)^{2}}{x} dx

STEP 7

Now, we see that the integral on the right side is the same as the original integral. Let's denote the original integral as '':
=(lnx)32 = (\ln x)^{3} -2

STEP 8

olve the equation for '':
3=(lnx)33 = (\ln x)^{3}=13(lnx)3 = \frac{1}{3}(\ln x)^{3}So, the solution to the integral (lnx)2xdx\int \frac{(\ln x)^{2}}{x} dx is 13(lnx)3\frac{1}{3}(\ln x)^{3}.

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