What is a quadrilateral?
A quadrilateral consists of four points. The sum of its angles is always .
In the following we show some special quadrilaterals that have their own names.
In a square, all sides have equal lengths and all angles are .
All angles are and opposite sides have equal length.
Opposite sides have equal length and are parallel but unlike the rectangle, the angles can have values other than . Opposite angles are equal.
Two opposite sides are parallel.
Opposite sides have equal length and are parallel. Unlike the square, the angles can have values other than . Opposite angles are equal.
The diagonals are perpendicular to each other and both pairs of adjacent sides have equal length.