Test and analysis: If the center of the inscribed spherical surface of a tetrahedron is O, then the distance from the center of the spherical surface O to the four surfaces is R. According to the method of solving the triangle area: division, connecting O with the four vertices, it can be obtained that the volume of the tetrahedron is equal to the sum of the volumes of four triangular pyramids with O as the vertex and four surfaces as the bottom respectively.

Comments: Analogical reasoning refers to analogizing the known properties of one type of mathematical object to another according to the similarity of two types of mathematical objects. The general steps to solve the problem of analogical reasoning are: ① to find out the similarity or consistency between two kinds of things; (2) use the nature of one kind of things to infer the nature of another kind of things, and get a clear proposition (or guess).