Teaching material of engineering mathematics in colleges and universities: mathematical physical equations and special functions (fourth edition) The fourth edition of teaching material of engineering mathematics in colleges and universities: mathematical physical equations and special functions (fourth edition) is revised on the basis of the third edition. Compared with the third edition, the main differences are: the third edition adds the section of "Fourier transform and Laplace transform", deletes the energy integration method in the seventh edition, simplifies and refines the nonlinear partial differential equation in the ninth edition (deletes some theoretical derivation and supplements physical explanation), and adds the difference solution (these contents are combined with variational method as the seventh chapter of the new edition). In addition, the contents and written expressions in the book have been revised and revised in detail, and several examples and notes have been added.