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Mathematics 8 Online
OpenStudy (anonymous):

Integrate: x(arctanx) dx

myininaya (myininaya):

\[\int\limits_{}^{}x \arctan(x) dx\] This is what I would do: make a substitution and then use integration by parts

OpenStudy (anonymous):

parts is it

OpenStudy (anonymous):

get \[\frac{1}{2}x^2\arctan(x)-\frac{1}{2}\int \frac{x^2}{x^2+1}dx\] pretty much in your head, but have fun with the second integral. i leave that for myininaya

OpenStudy (anonymous):

wow must be a hard one i would divide first

OpenStudy (anonymous):

get \[\int\frac{x}{x^2+1}dx=\int 1dx-\int \frac{1}{x^2+1}dx\] then i would take a break

OpenStudy (anonymous):

alright, so like long division?

OpenStudy (anonymous):

how did you get the first step? the one you got from your head?

OpenStudy (anonymous):

parts \[\int f dg =fg-\int gdf\] with \[f=tan^{-1}, dg = x, g =\frac{x^2}{2}, df =\frac{1}{x^2+1}\]

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