WEBVTT

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Here is the problem: integral of ln(x).

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Find the indefinite integral (antiderivative) of ln(x) with respect to x.

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Start with the integral.

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the integral of ln x dx equals x ln x minus x (integration by parts).

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Simplify and add the constant of integration.

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So the answer is x(ln(x) minus 1) plus C.

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An antiderivative F satisfies F prime of x equals f(x). Because the derivative of any constant is 0, every antiderivative differs by a constant C.

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Differentiated the answer and compared it with the integrand at 8 sample points, which checks out.