In order to consider areas of space, it is necessary to expand the concept of a set, the properties of a set make it possible to find limits on sections of space
At the point of space under study, the function may behave differently: it may not be defined, it may be continuous. or it may diverge. A limit is a way to study the behavior of a function at a given point.
Sometimes, for the simplicity of solving a problem, it becomes necessary to use coordinate systems other than Cartesian, for example, solving problems with circles is more convenient in polar coordinates, the trajectory of the satellite is spherical, and