Conversion of cartesian coordinates to polar coordinates

Click For Summary

Homework Help Overview

The discussion revolves around converting a double integral from Cartesian coordinates to polar coordinates. The original poster is seeking confirmation on the limits of integration in polar form after sketching the region of integration.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to determine the correct limits for theta in the polar form of the integral and expresses confusion regarding the area represented by the integral. Other participants question the relationship between the area of integration and the function being integrated.

Discussion Status

Participants are actively engaging with the original poster's concerns, with some providing clarifications about the nature of double integrals and their relation to area. There is an acknowledgment of the need to differentiate between the area of integration and the function being integrated.

Contextual Notes

The original poster mentions a specific integral and its limits, indicating a potential misunderstanding of the area represented by the integral in Cartesian coordinates compared to polar coordinates.

CostasDBD
Messages
2
Reaction score
0
1. Was wondering if anyone could help me confirm the polar limits of integration for the below double integral problem. The question itself is straight forward in cartesian coordinates, but in polar form, I'm a bit suspect of my theta limits after having sketched the it out. any help much appreciated.



2. Homework Equations

[tex]\int^{6}_{0}\int^{y}_{0}xdxdy[/tex]

in polar form:

[tex]\int^{\frac{\pi}{2}}_{\frac{\pi}{4}}\int^{6cosec\theta}_{0} r^{2}cos\theta dr d\theta[/tex]


The Attempt at a Solution



Using a trig substitution over pi/2 and pi/4, i get an answer of 36. it's just when i sketch it, i get a triangle which only has half that area. am i missing something obvious? cheers
 
Physics news on Phys.org
Welcome to PF!

Hi CostasDBD! Welcome to PF! :smile:

(have a pi: π and a theta: θ and an integral: ∫ :wink:)
CostasDBD said:
Using a trig substitution over pi/2 and pi/4, i get an answer of 36. it's just when i sketch it, i get a triangle which only has half that area. am i missing something obvious? cheers

Yup! :redface:

∫∫ x dxdy isn't the area! :wink:
 
Remember, the area of integration and the actual integration are 2 separate entities. Only when the function you're integrating over is f(x,y) = 1 is the integral equal to the area of your area of a double integration.
 
Thanks guys. funny what you pick up when you go back a few pages and have a quick read hey.
this forum is fantastic.
 

Similar threads

  • · Replies 19 ·
Replies
19
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 11 ·
Replies
11
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
Replies
7
Views
2K
  • · Replies 22 ·
Replies
22
Views
2K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 14 ·
Replies
14
Views
3K
Replies
3
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K