Man pages matching name al_triangulate_polygon in section 3alleg5:

al_triangulate_polygon.3alleg5.en	debian 10 / allegro5-doc
al_triangulate_polygon.3alleg5.en	debian 11 / allegro5-doc
al_triangulate_polygon.3alleg5.en	debian 12 / allegro5-doc
al_triangulate_polygon.3alleg5.en	debian 13 / allegro5-doc