# Summary

- Sum of the angles of a quadrilateral is 360Â°.
- A diagonal of a parallelogram divides it into two congruent triangles.
- In a parallelogram,

(i) opposite sides are equal

(ii) opposite angles are equal

(iii) diagonals bisect each other - A quadrilateral is a parallelogram, if

(i) opposite sides are equal

(ii) opposite angles are equal

(iii) diagonals bisect each other

(iv) a pair of opposite sides is equal and parallel - Diagonals of a rectangle bisect each other and are equal and vice-versa.
- Diagonals of a rhombus bisect each other at right angles and vice-versa.
- Diagonals of a square bisect each other at right angles and are equal, and vice-versa.
- The line-segment joining the midpoints of any two sides of a triangle is parallel to the third side and is half of it.
- A line through the mid-point of a side of a triangle parallel to another side bisects the third side.
- The quadrilateral formed by joining the midpoints of the sides of a quadrilateral, is a parallelogram.

Â**Rectangle**A quadrilateral with all angles 90 degrees **Parallelogram**A quadrilateral with both pairs of opposite sides parallel **Rhombus**A quadrilateral with all sides equal **Square**A rectangle with all sides equal **Trapezium**A quadrilateral with one pair of opposite sides parallel **Kite**A quadrilateral with two pairs of adjacent sides of equal length