Quadrilateral

What is a quadrilateral?

A simple closed curve or a polygon formed by four line-segments or sides is called a quadrilateral.

The four line-segments forming a quadrilateral are called its sides.

For example - squares, rectangles, rhombuses, trapeziums and parallelograms are quadrilaterals.

A quadrilateral has four sides and four angles.

The symbol of a quadrilateral is .

Each shape shown below is a quadrilateral.

What is a Quadrilateral?



(i) Shape (d) is a special type of quadrilateral. Its opposite sides are equal. Each angle of it is a right angle. Its name is rectangle.

Shape of a Rectangle

AB = CD, AD = BC and ∠DAB = ∠ABC = ∠BCD = ∠CDA = 90°.



(ii) The quadrilateral (e) is named as square. All the sides of it are of equal measure and each angle is a right angle.

Shape of a Square

In the above figure, AB = BC = CD = DA and ∠ABC = ∠BCD = ∠DAB = ∠CDA = 90°.



(iii) Shape (f) is a quadrilateral having the special name parallelogram and with opposite sides equal and parallel.

It has also its opposite angles equal.

Shape of a Parallelogram

In the above figure, AB and CD are equal and parallel. Similarly, AD and BC are equal and parallel.

∠DAB = ∠DCB and ∠CDA = ∠CBA.



(iv) Shape (g) is the shape of a rhombus whose all sides are equal.

A rhombus is a parallelogram with all its sides equal.

Its two opposite angles are equal and greater than 90°. Its other two opposite angles are equal and less than 90°.

Note: A rhombus cannot have any right angle.

Shape of a Rhombus

In the above figure, AB = BC = CD = DA. AB is parallel to CD and AD is parallel to BC.

∠DAB = ∠DCB and ∠CDA = ∠CBA

No angle is right angle.



(v) The quadrilateral (h) is the shape of a trapezium.

A trapezium is a quadrilateral which has a pair of opposite sides parallel.

Shape of a Trapezium

In the above figure, opposite sides AB and CD are parallel.



A polygon covers a plane space whose area may be calculated. The length of the covering sides is called its perimeter.

Note: The sum of angles of a quadrilateral is always 360°.

Related Concepts on Geometry - Simple Shapes & Circle

Simple Closed Curves

Polygon

Different Types of Polygons

Angle

Triangle

Quadrilateral

Circle Math

Line Symmetry

Symmetrical Shapes


4th Grade Math Activities

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