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 Quadrilateral :
9. Types of Quadrilaterals
(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 900 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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