Parallelogram

From AoPSWiki

A parallelogram is a quadrilateral in which both pairs of opposite sides are parallel. Its properties include:

• Opposite sides are parallel.

• Opposite sides are congruent.

• Opposite angles are congruent.

• Consecutive angles are supplementary.

• Diagonals bisect each other.

• Each diagonal divides the figure into 2 congruent triangles.

• Both diagonals together divide the figure into 2 pairs of congruent triangles. All 4 triangles have equal area.

Common Parallelograms

• Rectangle

• Square

• Rhombus