# Introduction to Quadrilateral

In introduction to quadrilateral, we will learn the basics about the quadrilateral.The word ‘quad’ means four and the word lateral means sides. Thus, a plane figure bounded by four line segments AB, BC, CD and DA is called a quadrilateral and is written as quad. ABCD.

**Vertices**

**Sides**

i) A i) AB

ii) B ii) BC

iii) C iii) CD

iv) D iv) DA

**Angles**

**Diagonals**

i) ∠A i) AC

ii) ∠B ii) BD

iii) ∠C

iv) ∠D

On the basis of diagonals, there are two types of quadrilaterals.

1) Convex

2) Concave

In

**Convex quadrilateral**, the diagonals intersect in the

**interior region**and in

**Concave quadrilateral**, one of the diagonal is in the

**exterior region**.

**Various Parts of Quadrilateral**

**1) Adjacent sides :**Two sides of a quadrilateral are called adjacent sides, if they have a common end point.

According to the given diagram, the adjacent sides are

i) AB, BC

ii) BC, CD

iii) CD, DA

iv) DA, AB

**2) Opposite sides :**Two sides of a quadrilateral are called its opposite sides, if they do not have a common end point.

i) AB and CD

ii) AD and BC

are two pairs of opposite sides of the quadrilateral ABCD.

**Diagonals :**It is formed by the segment joined by the opposite vertices.

AC and BD are diagonals.

**Adjacent angles :**Two angles of a quadrilateral are called adjacent angles, if they have a common side as an arm.

i) ∠A , ∠B

ii) ∠B, ∠C

iii) ∠C , ∠D

iv) ∠D , ∠ A

are four adjacent angles.

**Opposite angles :**Two angles of a quadrilateral are called opposite angles which are not adjacent angles.

i) ∠A , ∠C

ii) ∠B , ∠D are two pairs of opposite angles of the quadrilateral ABCD.

**Quadrilateral**

• Introduction to Quadrilateral

• Types of Quadrilateral

• Properties of Quadrilateral

• Parallelogram and its Theorems

• Rectangle and its Theorems

• Square and its Theorems

• Rhombus and its Theorems

• Trapezoid (Trapezium)and its Theorems

• Kite and its Theorems

• Mid Point Theorem

• Introduction to Quadrilateral

• Types of Quadrilateral

• Properties of Quadrilateral

• Parallelogram and its Theorems

• Rectangle and its Theorems

• Square and its Theorems

• Rhombus and its Theorems

• Trapezoid (Trapezium)and its Theorems

• Kite and its Theorems

• Mid Point Theorem