[justify]A plane convex quadrilateral is a rectangle if, and only if, all four angles are congruent. [br][b]Note: Since all four angles are congruent and the sum of the internal angles of the quadrilateral is 360º, then each angle measures 90º.[/b][/justify]
In every rectangle, all diagonals are congruent.[br]
Research and prove the argument of following property: Every parallelogram that has congruent diagonals is a rectangle."