Sum of the interior angles of a polygon

Investigate the relationship between the number of sides a polygon has and the sum of its interior angles.

Sum of the interior angles for quadrilaterals

1. What is the sum of the interior angles for quadrilaterals?

2. What is the sum of the interior angles for any pentagon?

3. What is the algebraic expression that represents the sum of the interior angles of a polygon that has n sides?

4. What is the sum of the interior angles of a dodecagon?