## 1. Quadrilateral : A plane figure bounded by four line segments is called quadrilaterals.

2. Sides of Quadrilateral :

3. Diagonals of Quadrilateral :

4. Adjacent Sides of Quadrilateral :

5. Opposite Sides of Quadrilateral :

6. Consecutive Angles of Quadrilateral :

7. Opposite Angles of Quadrilateral :

8. Sum of four Angles QuadrilateralÂ :

9. Types of QuadrilateralsÂ

(i). Parallelogram : A quadrilateral in which opposite sides are parallel is called Parallelogram

Properties of Parallelogram :

(ii). Rectangle : A parallelogram each of whose angle is 90^{0} is called a Rectangle.

Properties of Rectangle :

(iii). Square : A rectangle having all side equal is called a Square.

Properties of Square :

(iv). Rhombus : A parallelogram having all side equal is called a Rhombus.

Properties of Rhombus :

(v). Trapezium : A quadrilateral in which two opposite sides are parallel and two opposite sides are non – parallel is called a Trapezium.

(vi). Kite : A quadrilateral in which two pairs of adjacent side are equal is known as kite.

10. Intercept Theorem : If there are three parallel lines and the intercepts made by them on one transversal are equal them the intercepts on any other transversal are also equal.

11. Midpoint Theorem : The line segment joining the midpoint of any two sides of a triangle is parallel to the third side and equal to half of it.

12. Converse of Midpoint Theorem : The line drawn through the midpoint of one side of a triangle , parallel to another side , intersects the third side at its midpoint.

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