Perimeter and Area of Parallelograms
Parallelograms are quadrilaterals whose opposite sides are parallel. There opposite angles are congruent.
A rhombus is a special parallelogram with all four sides congruent.
When all angles of a rhombus are 90°, it is a square.
When all angles are 90° and opposite sides are congruent, it is a rectangle.
If you want to work with squares or rectangles, click Angle until you get a 90° angle.
Hence, parallelograms may have multiple names depending upon the values of their angles and/or sides.