1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
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: Line Integral

  1. May 31, 2010 #1
    1. The problem statement, all variables and given/known data

    http://www.maths.ox.ac.uk/system/files/private/active/0/b05.pdf [Broken]
    Q8, last part


    2. Relevant equations



    3. The attempt at a solution

    Essentially we are calculating the integral of -dG/dn*g(x,y) ds

    I'm pretty sure G is (1/2Pi)log((x-e)^2+(y-m)^2) (using e,m instead of greek letters)

    I can't get the integral to come out. Essentially I end up with the correct denominator but ((2x-2e)cost+(2y-2m)sint)g(cost,sint) as the numerator.

    This can be rearranged to 2(1-ecost-msint)g, I seem to have picked up a factor of -2 and I need to convert this cost and sint to e and m respectively.

    I've let x=cost y=sint and replaced ds by dt and integrating between 0 and 2Pi.

    In working out dG/dn, I'm using dG/dn=dG/dxcost+dG/dysint

    I don't know where I'm going wrong. I'm probably making a very basic error so even if you don't know what Green's functions are you may spot my mistake.

    Thanks
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted