1, A 1 mainly refers to differentiation, A2 mainly refers to integration, and A3 has a wide range: series, complex variable function, matrix, probability theory, etc. 2. Calculus is a branch of mathematics that studies the differentiation, integration and related concepts and applications of functions in higher mathematics. It is the basic subject of mathematics. The content mainly includes limit, differential calculus, integral calculus and its application. Differential calculus, including the calculation of derivatives, is a set of theories about the rate of change. It makes the function, velocity, acceleration and curve slope can be discussed with a set of universal symbols. Integral calculus, including the calculation of integral, provides a set of general methods for defining and calculating area and volume.