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Differentiation C3. Watch

1. Hey,

How would I integrate x^2*tan^-1x?? I'm stuck on what to do with the x^2 bit. I know that tan^-1x gives 1/(1+x^2). Thanks.
2. Are you integrating or differentiating? I'm guessing you mean differentiating because you can't integrate that function.

Use the product rule, letting x^2=u and tan^-1x=v. You know dv/dx because you just posted it, and du/dx is just 2x.

u(dv/dx) + v(du/dx) = x^2(1/(1+x^2)) + (tan^-1x)2x

and you can re-order the terms a bit to make this look nicer.
3. If you are integrating, why not just use integration by parts?
4. (Original post by ttoby)
Are you integrating or differentiating? I'm guessing you mean differentiating because you can't integrate that function.
http://www.wolframalpha.com/input/?i...ate+x^2arctanx
5. +1

Thought I'd gone crazy for a second, was about to consult Wolfram myself!
6. Can anyone help me, I haven't got a clue what to do.
7. (Original post by FutureMedic)
Can anyone help me, I haven't got a clue what to do.
Are you 100% certain that is what you're trying to work out? Integration by parts is the way to do it but the integral of definitely wasn't on my C3 syllabus...
8. Good point. I'm sure I typed it into Wolfram Alpha myself but I must have typed it wrong. +rep
9. (Original post by chigley)
Are you 100% certain that is what you're trying to work out? Integration by parts is the way to do it but the integral of definitely wasn't on my C3 syllabus...
Oh, not integrate... differentiate. :P Sorry.
10. (Original post by FutureMedic)
Oh, not integrate... differentiate. :P Sorry.
Just use product rule
if equation is in the form
y=uv
dy/dx=u'v+uv'

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