Theorems of limit existence criterion include: pinch theorem, monotone bounded criterion and Cauchy criterion. The limits of some functions are difficult or difficult to be obtained directly by limit algorithm, and need to be determined first. Here are several commonly used theorems to determine the limit of a sequence.

Math:

Mathematics is a subject that studies concepts such as quantity, structure, change, space and information. Mathematics is a universal means for human beings to strictly describe the abstract structure and mode of things, and can be applied to any problem in the real world. All mathematical objects are artificially defined in essence. In this sense, mathematics belongs to formal science, not natural science. Different mathematicians and philosophers have a series of views on the exact scope and definition of mathematics.