If you want to improve your class 9 Math, Quadrilaterals concepts, then it is super important for you to learn and understand all the formulas.

By using these formulas you will learn about the Quadrilaterals.

With the help of these formulas, you can revise the entire chapter easily.

## Quadrilaterals Class 9 Maths Formulas

**Quadrilateral:**A plane figure bounded by four line segments is called quadrilateral.

In quadrilateral $\mathrm{ABCD}, \mathrm{AB}, \mathrm{BC}, \mathrm{CD}$ and $\mathrm{DA}$ are sides; $\mathrm{AC}$ and $\mathrm{BD}$ are diagonals and $\angle \mathrm{ABC}+\angle \mathrm{BCD}+\angle \mathrm{CDA}+\angle \mathrm{DAB}=360^{\circ} .$

**Quadrilaterals Types**

- Parallelogram: A quadrilateral whose each pair of opposite sides are parallel.
- Rectangle: A parallelogram whose one angle is 90°. Diagonals are equal.
- Rhombus: A parallelogram whose adjacent sides are equal. Note: Diagonal bisect each other at 90°.
- Square: A rectangle whose adjacent sides are equal (four sides are equal). Diagonal bisect each other at 90°.
- Trapezium: A quadrilateral whose one pair of opposite sides are parallel. AB || DC
- Kite: It has two pair of adjacent sides that are equal in length but opposite sides are unequal.

**Properties of a Parallelogram**

- Opposite sides are equal. e.g., AB = DC and AD = BC
- Consecutive angles are supplementary. e.g., $\angle \mathrm{A}+\angle \mathrm{D}=180^{\circ}$
- Diagonals of parallelogram bisect each other.
- Diagonal divide it into two congruent triangles. A B

**Quadrilaterals Theorem**

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

Also Read,

Download NCERT Class 9 Maths Book in PDF

Download NCERT Class 9 Science Book in PDF

Download NCERT Class 9 Science Exemplar in PDF

Download NCERT Class 9 Maths Exemplar in PDF

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