Watch this video to learn how to find the area of quadrilaterals. A garden is in the shape of a rectangle measuring \(16.3m\) by \(12.4m\). The gardener marks out the two diagonals and decides to ...

is the number of sides. Another way to calculate the sum of the interior angles of a polygon is to see how many triangles the shape is composed of. Quadrilaterals are composed of two triangles.