## Online Course Discussion Forum

### MC I-C problem 7.26

You just need to verify it. That is, you will need to count the number of faces ($F$), vertices ($V$), and edges ($E$) of the regular octahedron, and verify that indeed $V - A + F = 2$.

For this purpose a picture is not needed, since we know it is formed by $8$ equilateral triangles. (Think of two square pyramids glued together by their square faces.)

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