Characterizations
A convex quadrilateral is a rectangle if and only if it is any one of the following:
- a parallelogram with at least one right angle
- an equiangular parallelogram
- a parallelogram with diagonals of equal length
- a parallelogram ABCD where triangles ABD and DCA are congruent
- a quadrilateral which has four right angles
- an equiangular quadrilateral
Read more about this topic: Rectangle