Explanation

A polygon with 8 sides has 8 vertices. To form a triangle, you need to choose 3 vertices out of these 8. This can be done in:

8C3 = 8! / (3! x (8-3)!)

= 8! / (3! x 5!)

= (8 x 7 x 6) / (3 x 2 x 1)

= 56

So, 56 triangles can be formed by joining the angular points of a polygon with 8 sides.