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.

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

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.