- #1
insynC
- 68
- 0
I asked a question earlier about Calculus of Variation, but the question I gave didn't really highlight my confusion well. I've come across some other questions that I think reveal my misunderstanding.
Solve the Euler equation for the following integral:
(integral from x1->x2) ∫[(y')² + √y]dx
Euler equation:
∂F/∂y - d/dx (∂F/∂y') = 0
F = (y')² + √y
So ∂F/∂y = 1/[2√y] and d/dx (∂F/∂y') = 2y'
Thus: y'' = 1/[4√y]
Although it has been some time since I took an ODE course, I think that the equation above is non-trivial to solve. So either I'm mistaken and this is easy to solve or I'm going about the calculus of variations method mistakenly.
With a similar problem, ∫[1+yy']²dx, I was only able to reduce it down to: y''y² + y(y')² = 0, which again I couldn't solve.
I'm not looking for answers, just want to know where I'm applying the method incorrectly, or if in fact I'm missing a far easier way to apply it.
Thanks for any help!
Homework Statement
Solve the Euler equation for the following integral:
(integral from x1->x2) ∫[(y')² + √y]dx
Homework Equations
Euler equation:
∂F/∂y - d/dx (∂F/∂y') = 0
The Attempt at a Solution
F = (y')² + √y
So ∂F/∂y = 1/[2√y] and d/dx (∂F/∂y') = 2y'
Thus: y'' = 1/[4√y]
Although it has been some time since I took an ODE course, I think that the equation above is non-trivial to solve. So either I'm mistaken and this is easy to solve or I'm going about the calculus of variations method mistakenly.
With a similar problem, ∫[1+yy']²dx, I was only able to reduce it down to: y''y² + y(y')² = 0, which again I couldn't solve.
I'm not looking for answers, just want to know where I'm applying the method incorrectly, or if in fact I'm missing a far easier way to apply it.
Thanks for any help!