You are Here: Home >< Maths

# Integral help watch

1. Any good method for this?
(please attach I do not have home-works any more!!!)

I have the correct answer (which is part of an undergrad question to which I am writing a solution)
It is just that the method seems a bit too long and I do not want to rewrite the solution as this integral lies somewhere in the middle of a longish problem

Thanks
Attached Images

2. TeeEm needing help?!? Thought I'd never see the day! :P
3. Integration by parts?
4. (Original post by iMacJack)
TeeEm needing help?!? Thought I'd never see the day! :P
happens to me more regularly than I would like to admit ...

However in this question I have done the integral without problems; I just look for a quicker alternative if it exists.
( it is just that I am doing high level maths non-stop since this morning and my brain is now stalling )
5. (Original post by ubisoft)
Integration by parts?
I second that idea...and so does Wolfram Alpha 🙂
6. (Original post by TeeEm)
happens to me more regularly than I would like to admit ...

However in this question I have done the integral without problems; I just look for a quicker alternative if it exists.
( it is just that I am doing high level maths non-stop since this morning and my brain is now stalling )
Lol! Fair enough man. My brain gets fried from too much FP1, so you're not doing too badly :P Keep up the good work man
7. (Original post by Gregorius)
I second that idea...and so does Wolfram Alpha 🙂
I split the log

the second part I left alone

The first part of the log
I did substitution x = 2tantheta for the first part of the log
then parts

then combined all into the answer

EDIT No need for substitution/ direct parts cuts the work a bit/ good enough
8. (Original post by TeeEm)
I split the log
Mathematical lumberjack as well now!
9. (Original post by Gregorius)
Mathematical lumberjack as well now!
I cut a bit of the work out now, so it is ok...

It is actually one of the questions you posed the other night, that I took and made a question out of ...

Find

INTEGRAL (sin2x/x2) from 0 to infinity, using Laplace transform techniques
10. (Original post by Gregorius)
Mathematical lumberjack as well now!
(Original post by TeeEm)
I cut a bit of the work out now, so it is ok...

It is actually one of the questions you posed the other night, that I took and made a question out of ...

Find

INTEGRAL (sin2x/x2) from 0 to infinity, using Laplace transform techniques
This reminds me, Greogrius - I tried computing a recurrence for the integral of nth powers of the since function, i.e a closed form for and eventually gave up (although I managed to get the first few nth powers, up to 5 or so) - then a quick math.stackexchange lookup yielded and impressive and complex-looking closed form!
11. (Original post by Zacken)
This reminds me, Greogrius - I tried computing a recurrence for the integral of nth powers of the since function, i.e a closed form for and eventually gave up (although I managed to get the first few nth powers, up to 5 or so) - then a quick math.stackexchange lookup yielded and impressive and complex-looking closed form!
I just borrowed the n=2 case to make a question for my LaplaceTransform resources
12. (Original post by TeeEm)
I just borrowed the n=2 case to make a question for my LaplaceTransform resources
I saw - I really need to brush up on my Laplace Transforms, perhaps starting with your resources! :-)
13. (Original post by Zacken)
This reminds me, Greogrius - I tried computing a recurrence for the integral of nth powers of the since function, i.e a closed form for and eventually gave up (although I managed to get the first few nth powers, up to 5 or so) - then a quick math.stackexchange lookup yielded and impressive and complex-looking closed form!
Ooh! Do you have a link to the math.stackexchange article?
14. (Original post by Gregorius)
Ooh! Do you have a link to the math.stackexchange article?
Here you go, although most of the information/maths is in the PDFs/papers that they've linked to in the comments. :-)
15. (Original post by TeeEm)
Any good method for this?
(please attach I do not have home-works any more!!!)

I have the correct answer (which is part of an undergrad question to which I am writing a solution)
It is just that the method seems a bit too long and I do not want to rewrite the solution as this integral lies somewhere in the middle of a longish problem

Thanks

Let

So:

Now by parts we have:

Now so:

(Confirmed by Wolfram)
16. (Original post by Zacken)
I saw - I really need to brush up on my Laplace Transforms, perhaps starting with your resources! :-)
I wrote many questions last week as I am helping 2 students at present,

wait until I update the site as none of them are there

here is the one I made tonight which lead to this integral
Attached Images

17. (Original post by Zacken)
Here you go, although most of the information/maths is in the PDFs/papers that they've linked to in the comments. :-)
Excellent! An endless stream of exam questions for the future!
18. (Original post by Gregorius)
Excellent! An endless stream of exam questions for the future!
Poor students.
19. (Original post by TeeEm)
I wrote many questions last week as I am helping 2 students at present,

wait until I update the site as none of them are there

here is the one I made tonight which lead to this integral
Thanks for this! :-)
20. (Original post by atsruser)

Let

So:

Now by parts we have:

Now so:

(Confirmed by Wolfram)
Thank you

I originally did that way but I did it directly by parts ( a tiny bit quicker)
I was just wondering if there was an obvious method (as I am very tired) and this was part of a solution so I did not want to redo it at a later stage.

### Related university courses

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: November 11, 2015
Today on TSR

### Edexcel C2 Core Unofficial Markscheme!

Find out how you've done here

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams