Question

quadrilateral ABCD has
Four sides, namely AB,BC, CD and DA
Four vertices, namely A, B, C and D.
Four angles, namely ZABC, ZBCD, CDA and ZDAC.
The line segments joining the opposite vertices of a quadri-
lateral are called the diagonals of the quadrilateral. AC and
of) BD are the diagonals of quadrilateral ABCD.
ctive
The two sides of a quadrilateral which have a common vertex are called the adjacent
sides' of the quadrilateral. In quadrilateral ABCD, AB is adjacent to BC and B is their
common vertex
The two angles of a quadrilateral having a common side are called the pair of'adjacent
angles' of the quadrilateral. Thus, ZABC and BCD are a pair of adjacent angles and
BC is the common side
Do This
1. Find the other adjacent sides and common vertices.​

Answer 1

Answer:

A simple closed figure formed by joining four line segments is called a quadrilateral.

It has 4 sides, 4 angles, 4 vertices and two diagonals.

In a quadrilateral if A, B, C, D are four points in a plane such that no three of them are collinear and the line segments AB, BC, CD and DA do not intersect except at their end points. Then, the figure formed by these four line segments is called the quadrilateral ABCD.



In a quadrilateral ABCD ..

(i) the four points A, B, C, D are called its vertices,

(ii) the four line segments AB, BC, CD and DA are called its sides,

(iii) ∠DAB, ∠ABC, ∠BCD and ∠CDA are called its angles, to be denoted by ∠A, ∠B, ∠C and ∠D respectively, and

(iv) the line segments AC and BD are called its diagonals.

Convex Quadrilaterals and Concave Quadrilaterals:

If each angle of the quadrilateral is less than 180°, it is called a convex quadrilateral.



1Save

If at least one angle of the quadrilateral is more than 180°, it is called a concave quadrilateral.



1Save

Note:

This figure is not a quadrilateral because it is not a simple closed figure.



1Save

Sides, Angles, Vertices, Diagonals of the Quadrilateral: