CBSE Class 09 Mathematics

Revision Notes
CHAPTER 8

• Angle Sum Property of a Quadrilaterals
• Properties of a Parallelogram
• The Mid-point Theorem

1. Sum of the  all angles of a quadrilateral is ${360}^{o}$
2. A diagonals of a parallelogram divides it into two congruent triangles.
3. In a parallelogram
• diagonals bisects each other.
• opposite angles are equal.
• opposite sides are equal

(4) Diagonals of a square bisects each other at right angles and are equal, and vice-versa.
(5) A line through the mid-point of a side of a triangle parallel to another side bisects the third side. (Mid point theorem)
(6)The line segment joining the mid-points of two sides of a triangle is parallel to the third side and equal to half the third side.
(7) In a parallelogram, the bisectors of any two consecutive angles intersect at right angle.
(8) If a diagonal of a parallelogram bisect one of the angles of a parallelogram it also bisects the second angle.
(9) The angle bisectors of a parallelogram form a rectangle.
(10) Each of the four angles of a rectangle is right angle.
(11) The diagonals of a rhombus are perpendicular to each other.