Area of a polygon — lesson. Mathematics CBSE, Class 8.

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A polygon is any shape with a minimum of three sides.

Let us consider the following pentagon

$ABCDE$ and try to find its area.

Area of a pentagon can be found in two ways.

Type

$1$

Let us use the method of triangulation using two diagonals.

Let us look at the figure given below for a better understanding.

$\text{Area of a pentagon} = \text{Area of}$

$\triangle AED + \text{Area of}$

$\triangle ABD + \text{Area of}$

$\triangle BCD$

Type

$2$

Another way of obtaining the area of a pentagon is by drawing one diagonal and drawing two perpendiculars to that diagonal.

Let us look at the figure given below for a better understanding.

In the figure given above,

$BD$ is the diagonal,

$EO$ and

$AN$ are the two perpendiculars to

$BD$ .

Here,

$\text{Area of a pentagon} = \text{Area of}$

$\triangle ODE + \text{Area of}$

$\triangle BCD + \text{Area of trapezium}$

$AEON + \text{Area of}$

$\triangle ABN$

Did you find an error?

3. Area of a polygon