# Parallelogram

From Knowino

A **parallelogram** is a planar figure bounded by four straight lines (a quadrilateral) in which both pairs of opposite sides are parallel.

It can be proved that in any parallelogram opposite sides and opposite angles are equal. Each diagonal divides the parallelogram into two congruent triangles.

In the figure line segment *AB* is parallel to *DC* and *AD* is parallel to *BC*.
Further *AB* is equal to *DC* (segments have same length) and *AD* is equal to *BC*. The angle ∠*DAB* is equal to ∠*BCD* and ∠*ADC* is equal to ∠*CBA*. The triangle *ABD* is congruent to *CDB* (two sides and included angle are respectively equal). Similarly, *DAC* is congruent to *BCA*.