Quadrilaterals

Quadrilaterals

Points to be Remember:-

1. If we take four points say A,  B, C, and D in a plane such that no

    three of them are collinear and the line segments AB, BC, CD and  

    DA intersect at their ends only, then the figure so formed by the

    four line segments is called a quadrilateral.

2. The points A,  B, C, and D are called the vertices of the

    quadrilateral ABCD.

3. The line segments AB, BC, CD and DA are called the sides of the

     quadrilateral ABCD.

4. The angles of the quadrilateral ABCD are ÐA, ÐB, ÐC, and ÐD.

5. The two line segments joining the opposite vertices are called the

    diagonals of the quadrilateral ABCD.

6. In a quadrilateral, two sides that have a common vertex are known

    as adjacent sides.

7. In a quadrilateral, any two sides that do not have a vertex in

    common are called opposite sides.

8. Two angles of a quadrilateral are adjacent angles, if they have a

    side of the quadrilateral as a common arm.

9. Two angles of a quadrilateral that are not adjacent are called

     opposite angles.

10. The interior of the quadrilateral ABCD, together with its boundary

       (i.e. the quadrilateral itself) is called the quadrilateral region

       ABCD.

11. The sum of the angle of a quadrilateral is 360°.