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! uncertain about direction.

  1. Feb 18, 2010 #1
    1. The problem statement, all variables and given/known data
    Evaluate [tex]\int[(3x-y)dx-xdy][/tex] where C consist of the parabola y=x^2 from (0,0) to (1,1) and then the line segment from (1,1) to (0,1)

    2. Relevant equations



    3. The attempt at a solution
    i did the integral of the y=x^2
    parametrized
    x=t
    y=t^2
    from 0 to 1
    then i got my 1/2
    but for the line segment do i just take the the integral using
    x=t
    y=1
    but for the interval do i use 0 to 1 or 1 to 0
     
    Last edited: Feb 18, 2010
  2. jcsd
  3. Feb 18, 2010 #2

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    You want to go from (1,1) to (0,1) along (t,1). That makes it t=1 to t=0, right?
     
  4. Feb 18, 2010 #3
    so would i get [tex]\int_1^0\\(3t-1)dt[/tex]
    and would i just integrate it like that
    i wouldnt require a negative because its a parametric correct?
     
  5. Feb 18, 2010 #4

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    Sure. You don't have to add any extra signs. Just work out what it is and add it to your first path.
     
  6. Feb 18, 2010 #5
    thanks for the help!
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook