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Euler Equation question

  1. Dec 13, 2009 #1
    1. The problem statement, all variables and given/known data
    This is a problem that the book uses as an example and Ive been trying since friday to get the same answer but i have not had any success, i need help :(

    Well in this problem, F = y(1+(y')^2)^1/2

    2. Relevant equations
    eulers eqn

    d/dx(partial(F)/partial(y')) - (partial(F)/partial(y)) = 0

    3. The attempt at a solution
    i get up to

    d/dx[y*y'/(1+(y')^2)^1/2)] - (1+(y')^2)^1/2 = 0

    but then the book loses me after doing some kind of reduction without showing the steps in between.

    after the reduction, they get: y*y"-((y')^2) -1 = 0

    could someone help me out with what they did in between? any help is appreciated
  2. jcsd
  3. Dec 13, 2009 #2
    Oh my god i am an idiot, i cant believe it took me this long to figure it out...

    Ignore thread =/
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