A quadrilateral is a figure having four sides, four angles and four vertices.

ANGLE SUM PROPERTY OF A QUADRILATERAL

This property states that the sum of the angles of a quadrilateral is 360^{o}.

PROPERTIES OF A PARALLELOGRAM

- A diagonal of a parallelogram divides it into two congruent triangles.
- In a parallelogram, opposite sides are equal.
- In a parallelogram, each pair of opposite sides is equal.
- In a parallelogram, opposite angles are equal.
- The diagonals of a parallelogram bisect each other.
- A quadrilateral is a parallelogram if a pair of opposite sides is equal and parallel.
- Mid-point theorem: The line segment joining the mid-points of two sides of a triangle is parallel to the third side.
- The line drawn through the mid-point of one side of a triangle, parallel to another side bisects the third side.