$$v-e+f=0$$$v-e+f=2$$where v is the number of vertices, e the number of edges and f the number of faces of a convex triagulated polyhedron in 3-space. 1 [made Community Wiki] Euler's classical formula for polyhedra$$v-e+f=0$$where$v$is the number of vertices,$e$the number of edges and$f$the number of faces of a triagulated polyhedron in$3\$-space.