Quadrilaterals Class 9 Notes – Chapter 9
What is a quadrilateral?
A quadrilateral is a closed figure with four straight sides. The sum of all the interior angles of a quadrilateral is 360 degree. Quadrilaterals Class 9 Notes are provided here to help learners prepare for their examination in an easy and effective manner.
The diagonal splits a parallelogram into 2 triangles which are congruent. Opposite sides and angles of a parallelogram are equal. Also, diagonals of a parallelogram always bisecting each other.
- A quadrilateral is a parallelogram, if either opposite sides or opposite angles are equal or diagonals are bisecting each other or pair of opposite sides are parallel and equal.
- In a rectangle, diagonals are equal and bisect each other and vice-versa.
- In a rhombus, diagonals bisect each other at 90 degree and vice-versa.
- In a square, diagonals are equal and bisect each other at 90 degree and vice-versa.
- In a triangle, the line joining midpoints of any two sides is parallel to the 3rd side and is half of it.
CBSE Revision Notes 