Place a square on a coordinate graph and label each vertex with variables. prove that the diagonals of a square are congruent and perpendicular to each other.

All quadrilaterals has a total measure of angle equal to 360 degrees. In the parallelogram ABCD, m<B = m<D = 41. So if m<B = m<D = 41, we have 41 + 41 = 82 degrees. Since the parallelogram is a quadrilateral, it has a total measure of angle of 360 degrees. So 360 – 82 is equal to 278 degrees. If the measure of angle C is equal to the measure of angle A, divide 278 by 2. We get 139 degrees. To confirm if the parallelogram ABCD has a total measure of 360 degrees, add 41 + 41 + 139 + 139 = 360 degrees.