Question

Using diagonals from a common vertex, how many triangles could be formed from the polygon pictured below?

Answer 1

9514 1404 393

Answer:

3

Explanation:

From a given vertex, two of the vertices are adjacent, so a "diagonal" to those will not form a triangle. The number of diagonals that can be drawn is 3 fewer than the number of sides. The number of triangles is 1 more than the number of diagonals.

For a 5-sided figure, 2 diagonals can be drawn from a common vertex.

3 triangles will be formed.