We can identify them by their vertices and slopes. Rectangles are quadrilaterals containing ony right angles. If the sides have equal lengths, then it ised a square. We can check that we have a rectangle by checking the slopes of the sides: they are parallel or perpendicular. Parallelogram are quadrilaterals with opposite .Learn to identify quadrilaterals such as kites, t.zoids, parallelograms, rhombuses, rectangles, and squares .Indeed SQUARES ARE RECTANGLES. All squares are rectangle, but not all rectanbles are squares. I will .Shape: Quadrilateral When we talk about "dissecting" a parallelogram and rearranging the parts to form a rectangle in order to determine the area of the parallelogram, we are clearly referring Elementary school curricula typi.y have children learn the names of special subsets of quadrilaterals with particular features..