Functions and Relations for an Evolving Star with Spherical Symmetry

In this paper, we drive and simplify some important equations and relations for an evolving star with spherical symmetry, and then give some simple analysis for their properties and implications. In the light-cone coordinate system, these equations and relations have a normal and neat form which is much accessible than the usual Einstein field equation. So they may be helpful for students to study general relativity and for researchers to do further discussion.