# Homework Help: 2D integral

1. Apr 15, 2006

### mmh37

Problem:

"Draw a Diagram to show over which area the following integral (see integral in attached file) is integrated."

I drew a little diagram of what I think the area looks like (see diagram). But I am very, very insecure about what I did and would appreciate if anyone could have a look at it and let me know if I did something wrong. That would be really helpful!

#### Attached Files:

File size:
8.1 KB
Views:
88
• ###### diagram.jpg
File size:
7.5 KB
Views:
106
2. Apr 15, 2006

### TD

I can't see the attachments yet, perhaps you could give the integral and the area? Try LaTeX

3. Apr 15, 2006

### mmh37

$$\int {2x^2+y} dxdy$$

and the boundary conditions are

for x: y < x < 2-y

for y: 0 < y < 1

hope that helps

4. Apr 15, 2006

### HallsofIvy

The outer integral is y so first draw to horizontal lines at y= 0 and y= 1 to define the limits for y. Now, for each y, x lies between y= x and x= 2- y which is the same as y= 2- x. However, in your picture you have x running between 0 and x. Move your stripes (indicating the figure) to the triangle formed by y= x, y= 2- x, and y= 0. (0f course, you notice that y= 2- x and y= x cross at y= 1.)

5. Apr 16, 2006

### mmh37

thanks for this!

I'm not sure whether this second attempt is right, but here is the new diagram anyway (with inverted strips):

File size:
13.9 KB
Views:
95