The above shown quadrilateral is a parallelogram in which all sides are equal. Also, one of the angles is
90∘. Hence it is a square.
The above shown quadrilateral is a parallellogram with one of its angles
90∘. Hence it is a rectangle.
The above shown quadrilateral is a parallelogram in which all the sides are equal and one of the angles is
75∘. Hence it is a rhombus.