Question

Calculus of Variations, Euler-Lagrange equation. Anybody can help? :)

Answer 1

I can somewhat

Answer 2

If we want to minimize the integral:
\[I=\int\limits_{x_1}^{x_2}f(y(x),y'(x),x)dx\]
We demand that:
\[\frac{\partial f}{\partial y}-\frac{d}{dx}\frac{\partial f}{\partial y'}=0\]