how to rotate a polygon around a vertex

hello guyz , i am a new user of the opengl GLUT library
and i wanna know how to rotate a polygon around a vertex and not the origin , using the glut library.
plz help

Move it so that the vertex you want to rotate around is the origin, rotate, move it back. This is independent of GLUT.

And please post a question only once.

assume that i want to move it around a vertex which coordinates are (20,60) how to do it like that , and without that vertex to the origin ?

As I told you, translate by (-20,-60), rotate, translate back (20,60). In the end this will also just be one transformation matrix for the GPU (that you can create on your own or by the old fixed-function glTranslate/glRotate/glTranslate calls).

Are you able to display your polygon and point yet without any rotation? If so, post your code. I think you’ll get a lot more help if you post your code and tell us exactly how far you’ve gotten so far. Remember to place the code inside

 and [\code] tags (except with a forward slash instead of a backslash).