Forced convergence, also known as pinch point theorem or double-sided pinch point rule, is one of the important methods to judge the convergence of function (sequence) and one of the concrete and effective methods to find the limit.

Mathematical analysis is the foundation and core of higher mathematics, which mainly studies concepts such as function, limit and calculus. In mathematical analysis, there is a very important and interesting theorem, called pinch theorem, also called double-sided pinch theorem, pinch criterion, pinch theorem, pinch theorem and sandwich theorem. The reason for this determination was put forward by French mathematician and physicist Lagrange in 1835. It can be used to solve some limit problems that seem complicated or difficult to calculate directly.