7-2. Definitions are one of the building blocks of geometric proofs. For example, by definition, a parallelogram is a quadrilateral with two pairs of parallel sides. You can use the definition of a parallelogram (or another polygon) as the starting point for proving other properties. a. Does the diagonal of a parallelogram always A B split the quadrilateral into two congruent triangles? Draw the diagram at right on your paper. If ABCD is a parallelogram, what do you know must be true from the definition? D O Mark the diagram appropriately and then write a flowchart proof to show that the triangles are congruent. b. Extend your flowchart proof from part (a) to prove that the opposite sides of a parallelogram are congruent