I need a textbook (or set of online lecture notes) on calculus of variation which focuses on the following topics "Variation of a functional, Euler-Lagrange equation, Necessary and sufficient conditions for extrema , Variational methods for boundary value problems in ordinary and partial differential equations"?please suggest a text book which contains more solved problems on the above topics .
what are the different methods to solve the boundary value problems in ordinary and partial differential equations?
I'm entirely new to this subject. Someone please help ...
