A fun fact about quadrilaterals, provable via some simple high school geometry, ... Quadrilaterals Contain Parallelograms: Varignon's Theorem. ByKevin Knudson, Former Contributor.

Parallelogram. A parallelogram is a quadrilateral where opposite sides are parallel and equal. Parallel sides are those that are moving in the same direction but are always equal distance apart.

The quadrilateral is a parallelogram. Opposite angles are equal. \({g}~=~50^\circ\) Angles in a quadrilateral add up to 360° and opposite angles are equal.

Learn about and revise angles, lines and multi-sided shapes and their properties with this BBC Bitesize GCSE Maths Edexcel study guide.