Consider a regular octagon. How many triangles can be formed whose vertices are the vertices of the octagon?
Label the vertices as {A, B,C,D,E,F,G,and H}
So, we want all the sets that consist of choosing any 3 of the 8 without regard to order...
So
C (8,3) = 56 triangles
Thanks, That really helps!
+470 
