im looking for any information about a builtin algorithm in opengl es to convert a 3d polygon in a triangle set. is there anything implemented like that in opengl es?
Short answer: No, not as a part of OpenGL ES.
Polygon tessellation is provided as part of the GLU (OpenGL Utility) library, on a per platform, per-version, per-implementer basis as it is optional rather than core to OpenGL.
If you are working on iPhone, you should have a look at iphone-glu which claims to support polygon tessellation.
Here's a more general walkthrough of using tessellation in OpenGL with GLU (not ES though) which might help illuminate your path.