Properties of angles of a convex polygon

An external angle of a convex polygon is an angle, adjacent to its internal angle.

Properties of triangle angles

1. The sum of the interior angles of a triangle is 180^∘.
2. The external angle of a triangle is equal to the sum of two internal angles that are not adjacent to it.

Properties of angles of a convex n-gon

A convex n-gon is a convex polygon with n sides.
3. Sum of the interior angles of an n-gon is 180^∘(n - 2).


4. Sum of the external angles of an n-gon is 360^∘.