Hello.I am a student and I am studying for physics olympiad.would you tell me what is the best book for learning lagrangian method ?

There's a great book called "Introduction to Classical Mechanics" (http://www.amazon.com/Introduction-Classical-Mechanics-Problems-Solutions/dp/0521876222/ref=sr_1_1?ie=UTF8&s=books&qid=1299382962&sr=8-1) by David Morin (Cambridge University Press) that does a great job explaining the Lagrangian Method as it applies to classical mechanics. In fact, the chapter on the Euler-Lagrange equations is one of a few that are available free on David Morin's website (http://www.people.fas.harvard.edu/~djmorin/chap6.pdf) at Harvard University.

If you want to learn more about Lagrangian mechanics or Hamiltonian mechanics, unfortunately I don't know what books are good or bad.

Good luck in the Olympiad! That's very impressive.

Thank you.I have that book.that is very nice.