## Euler characteristic

By *V,E,F* denote the number of vertices,
edges, and faces of a polyhedral solid. Then

*V-E+F=2.*

For example, a tetrahedron has *V=4,E=6,F=4*; for the cube the
numbers are *V=8,E=12,F=6*

Check the formula for the dodecahedron and for the soccer ball pictured here!