. Interior angles of a quadrilateral
There are 4 interior angles in a quadrilateral and they add up to a sum of 360°. This value is obtained by using the the angle sum property of a quadrilateral. According to the angle sum property of a polygon and the sum of the interior angles of a polygon will be calculated with the help of the number of triangles that can be formed in it. These triangles are formed by diagonals from a single vertex. To make this easier, this will be calculated by a formula, which says that if a polygon has 'n' sides, there will be (n - 2) triangles.