(a) In the parallelogram if the diagonal of the quadrilateral divides the quadrilateral into congruent triangles with the same size. These two parallel sides of parallelogram have some properties that are: The opposite or facing sides of the parallelogram has the equal length. The opposite angles of a parallelogram are of equal in measure. Know More About :- Inverse Function Calculator How To Find The Area of A Parallelogram (b) The opposite sides of the parallelogram are equal in measure.