Math Is Fun Forum

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: INTEGRATION: Substitution and Integration by parts Rules HELP!!

Hi;

How did you go about getting this integral?

This one is a little too difficult for right now (turns out it equals arctan(x)) Are you sure you have the right problem? Did you mean

Last edited by bobbym (2009-08-04 07:06:13)

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Makaros

Guest

Re: INTEGRATION: Substitution and Integration by parts Rules HELP!!

The above integration is tan^-1 x +C
Correct?

Makaros

Guest

Re: INTEGRATION: Substitution and Integration by parts Rules HELP!!

Well the problem is:
0
∫ 2/(1+x^2) dx
-1

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: INTEGRATION: Substitution and Integration by parts Rules HELP!!

Okay then we have the 4 things we need for an IBP

Now using the formula:

Now with the intervals of integration of -1 , 0

Last edited by bobbym (2009-08-04 07:48:17)

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Makaros

Guest

Re: INTEGRATION: Substitution and Integration by parts Rules HELP!!

Correct it the right answer...

Your very good at math, )))

Mostly I understand how to do U substitution but once I see a fraction I dont know how to do it..
(((

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: INTEGRATION: Substitution and Integration by parts Rules HELP!!

Hi Makaros;

I am passable on a good day at maths and sometimes I get lucky. Glad to help a little.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Makaros

Guest

Re: INTEGRATION: Substitution and Integration by parts Rules HELP!!

Oh here, I got one more question,

Find 
2
∫  (x+1) dx
-2

How to solve it?

Sarah12

Guest

Re: INTEGRATION: Substitution and Integration by parts Rules HELP!!

Math,can be hard sometimes but your will get it,just keep trying.:)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: INTEGRATION: Substitution and Integration by parts Rules HELP!!

Hi Makaros;

Last edited by bobbym (2009-08-04 08:03:19)

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Makaros

Guest

Re: INTEGRATION: Substitution and Integration by parts Rules HELP!!

OK, taht is also correct)

how about this one:

∫ x^3 e^(-x^2/2)   dx    Note: -x to the square of 2 all devided by 2, NOT including e

It says At first I gotta use Substitution rule AND  than IBP

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: INTEGRATION: Substitution and Integration by parts Rules HELP!!

Hi Makaros;

For:

Use the substitution;

The new integral is:

Now use IBP.

Last edited by bobbym (2009-08-04 08:54:52)

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Makaros

Guest

Re: INTEGRATION: Substitution and Integration by parts Rules HELP!!

Hi, Can you expalin briefly how you got that new integral, step by step.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: INTEGRATION: Substitution and Integration by parts Rules HELP!!

Hi;

Use the substitution;

Now replace the x^2/2 with u

Now an x dx with a du

and an x^2 with a 2u

Now use IBP

Last edited by bobbym (2009-08-04 09:07:44)

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Makaros

Guest

Re: INTEGRATION: Substitution and Integration by parts Rules HELP!!

Ok, but where do you get x^2 = 2u  ???

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: INTEGRATION: Substitution and Integration by parts Rules HELP!!

Hi Makaros;

Solve for x^2 from this.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Makaros

Guest

Re: INTEGRATION: Substitution and Integration by parts Rules HELP!!

I get

(√u)/2 =x

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: INTEGRATION: Substitution and Integration by parts Rules HELP!!

Hi;

Now times both sides by 2.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Makaros

Guest

Re: INTEGRATION: Substitution and Integration by parts Rules HELP!!

Ok I get it not, may you continue witH IBP

Makaros

Guest

Re: INTEGRATION: Substitution and Integration by parts Rules HELP!!

Hi. do you mind helpig me with one more question. I truly got lost on that one.

∫ e^(√x)

It says I gott to find an appropirate substitution and than use IBP.

Would sooo appreciate it.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: INTEGRATION: Substitution and Integration by parts Rules HELP!!

Hi Makaros;

For the integral

Say:

The new integral is:

An easy one for IBP.

Last edited by bobbym (2009-08-04 12:41:37)

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.