Calculus of variations

I. M. Gelfand, S. V. Fomin9780486414485, 0486414485, 0131122924, 9780131122925

First six chapters include theory of fields and sufficient conditions for weak and strong extrema. Chapter 7 considers application of variation methods to systems with infinite degrees of freedom, and Chapter 8 deals with direct methods in the calculus of variations. Problems follow each chapter and the two appendices. Fresh, lively text is ideal for advanced undergraduate and graduate students in math and physics.