2. The types of convergence are convergence sequence, functional convergence, global convergence and local convergence.
3. A lot of convergence means that the function has a limit.
4. Function convergence criterion: the definition that a function converges to a certain point.
5. For any real number c, there exists a number greater than 0; For any two numbers A and B, it is satisfied that A minus B is greater than 0 and less than C. ..
6. The definition of convergence embodies the essence of mathematical analysis.