Generalising angles in polygons (Part 1)

Maths

How many internal triangles can be formed within a megagon?

How many internal triangles from a distinct point can be formed within an icosagon?

The general formula for working out the total interior angles in a n-sided polygon is...

Using the formula, if I wanted to work out the total interior angles for a 360-sided shape, it would be...

The total sum of the interior angles of two triangles would be equal to...

If I have a regular pentagon, how many triangles from one distinct point internally can I create?

If I have a regular pentagon, what would the total interior angles sum to?

If I have a regular octagon, how many triangles from one distinct point internally can I create?

If I have a regular octagon, what would the total interior angles sum to?