Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Double integral, polar coordinates

  1. Feb 16, 2010 #1
    1. The problem statement, all variables and given/known data

    Evaluate [tex]\int[/tex][tex]\int[/tex]T (x^2+y^2) dA, where T is the triangle with the vertices (0,0)(1,0)(1,1)

    2. Relevant equations



    3. The attempt at a solution

    [tex]\int[/tex] d[tex]\theta[/tex] [tex]\int[/tex] r^3 dr

    Thats how far I got, not really sure about boundries on r. First integrals boundrie should be 0 to pi/4. Is polar coordinates a good idea? Should I try some other change of variabel?

    Help is appreciated

    thanks!
     
  2. jcsd
  3. Feb 16, 2010 #2

    LCKurtz

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Polar coordinates can be made to work but they are not the natural way to work this problem. There are no circles involved in the region. Just set it up as a normal dydx integral.
     
  4. Feb 16, 2010 #3
    I wouldn't do this in polar, though the x^2+y^2 makes it tempting...

    Draw out the triangle and figure out the equations for the lines that make it up, use these lines as your bounds for your double integral.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook