Calculate certain variables of a parallelogram depending on the inputs provided. Opposite sides are parallel and opposite angles are equal it is a Parallelogram. Properties Of Parallelograms Charts Parallelogram How To Memorize Things Solving Equations Classify Quadrilateral as parallelogram A classic activity. . A parallelogram is a closed four-sided two-dimensional figure in which the opposite sides are parallel and equal in length. Designed with Geometers Sketchpad in mind. The Varignon parallelogram is a rectangle if and only if the diagonals of the quadrilateral are perpendicular that is if the quadrilateral is an orthodiagonal quadrilateral. And the diagonals p and q of a rhombus bisect each other at right angles. 169 For a self-crossing quadrilateral the Varignon parallelogram can degenerate to four collinear points forming a line segment traversed twice. A parallelogram is a quadrilateral with opposite sides parall