Parallelograms (other)

A general parallelogram is a quadrilateral with both pairs of opposite sides parallel, but it is not required to have right angles (like a rectangle) or all sides equal (like a rhombus). These are sometimes called 'oblique parallelograms.'

Important properties

• Opposite sides are equal in length.

• Opposite angles are equal.

• The diagonals bisect each other but are not necessarily equal.

• The sum of the squares of the sides equals the sum of the squares of the diagonals: $AB^2 + BC^2 + CD^2 + DA^2 = AC^2 + BD^2$.

• The area can be found using $A = ab \sin \theta$, where $a$ and $b$ are adjacent sides and $\theta$ is the angle between them.