# Double integral finding the area

1. Apr 8, 2012

### pb23me

1. The problem statement, all variables and given/known data
Use a double integral to find the area of the region bounded by the curve r= 1+sin(theta)?

2. Relevant equations

3. The attempt at a solution I can't figure out what theta is intregrated from. I've tried from -(pi)/2 -> +(pi)/2 and that doesnt work. I've also tried from 0-> 2(pi) and that doesnt work. I have no clue what im supposed to integrate theta to. I would really appreciate some help with this.

2. Apr 8, 2012

### SammyS

Staff Emeritus
Have you done a polar plot?

0 → 2π should give the right answer.

What does your integral look like ?

3. Apr 8, 2012

### pb23me

i put a picture up

File size:
13.6 KB
Views:
250
4. Apr 8, 2012

### SammyS

Staff Emeritus
$\displaystyle \int_0^{2\pi}\int_0^{1+\sin(\theta)}r\,dr\,d\theta$​

What do you get for tour final answer?

5. Apr 9, 2012

### pb23me

I get (3(pi) + 2)/2

6. Apr 9, 2012

### SammyS

Staff Emeritus
Where does the " + 2 " come from ... as in
(3(π) + 2)/2​
?

What do you get upon integration w.r.t. r ?

7. Apr 9, 2012

### pb23me

Oh I see what ive been doing now. When I evaluated theta at 0 I was getting -2. I forgot to multiply this by 1/2 which would have given me 3(pi)(-2+2)/2 or 3(pi)/2 for my final answer. Thank you so much for all of your help I was stuck on that problem for awhile.