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C4 integration....help!!!

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Reply 20

Mr M

Study Forum Helper

Original post by diane_h

Ahhhh..... THAT'S why I've been going around in circles and getting nowhere. By parts is
Int(U) dv = uv- INT(V) du?

Yes - in your version of IBP you should set:

u = x^2

dv = \sin x \, dx

After you do one application you will still have an integral left to evaluate that includes a product but this time just x instead of x^2. One more application sees you home.

Reply 21

diane_h

Original post by Mr M

Yes - in your version of IBP you should set:

u = x^2

dv = \sin x \, dx

After you do one application you will still have an integral left to evaluate that includes a product but this time just x instead of x^2. One more application sees you home.

Ohhh thank you.... I think we've done this in class but maybe not formally called it integration by parts and we've not been told when it's suitable to use. All our teacher seems to bang on about is integration by substitution, chain rule and implicit differentiation in terms of the calculus in this module!

Reply 22

Mr M

Study Forum Helper

Original post by diane_h

If you have an integral that contains a product where one of the terms is x, x^2 or ln x you are likely to need IBP.

Reply 23

L-B

Can someone help me with this question: (NOTE- by '^4' i mean to the power of 4)
Integral of sec^4 x dx. let u=tanx.

I got tanx+c but the answer at the back of my textbook is: tanx+1/3 tan^3 x +c.......... :s-smilie: