You are Here: Home >< Maths

# Greens Theorem watch

1. I need to find the area, A, of the shape bounded by the curve, C, where C is given parametrically by

In the working belew, where the integrals have no bounded it means they are over either the region or the curve.

I used greens theorem with p=x/2, q=-y/2 so

and I know I have gone wrong up to here as the above is a straightforward integral which comes to 0 (wolfram confirms this). Where have I gone wrong? I know from looking at the shaoe that it has non zero area.

EDIT: Anyone know why the latex looks funny? I don't want the last line so spaced out.
2. (Original post by james22)
...
Not an expert on this, but just from googling:

Also, there's a minor error in that

3. (Original post by ghostwalker)
Not an expert on this, but just from googling:

Also, there's a minor error in that

Really? That second equals sign is copied directly from my notes (the only difference between mine and the notes one is in the notes it specifies what the integral is over, but the only reason I didn't put that on mine is I don't know the latex for it).

Fixed that small error.
4. (Original post by james22)
Really? That second equals sign is copied directly from my notes (the only difference between mine and the notes one is in the notes it specifies what the integral is over, but the only reason I didn't put that on mine is I don't know the latex for it).
Found a reference Wiki

PS When you swap it round, it works.
5. Why doesn't my method work though?
6. Where is the q from? Do you have a link to it?
7. (Original post by twig)
Where is the q from? Do you have a link to it?
q is just a function, I pick x and y so that I would get dp/dx-dq/dy=1.
8. (Original post by james22)
Why doesn't my method work though?
Not sure why you expect it to work. What do your notes say - need a scan/photo, with preamble.
9. http://www.maths.ox.ac.uk/system/fil...lectures10.pdf

Page 83 theorem 7.5
10. (Original post by james22)
You have p and q the other way about to the course material.
11. (Original post by ghostwalker)
You have p and q the other way about to the course material.
Thanks for that, I'll give it a go now and see what I get. That may well be what was causing the problems.
12. Yep, that worked. Thanks.
13. (Original post by james22)
q is just a function, I pick x and y so that I would get dp/dx-dq/dy=1.
Sorry, by q I meant the question! Haha.

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: April 2, 2013
Today on TSR

### University open days

• University of Warwick
Sat, 20 Oct '18
• University of Sheffield
Sat, 20 Oct '18
• Edge Hill University
Faculty of Health and Social Care Undergraduate
Sat, 20 Oct '18
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