Given the area of the sector of radius 6cm and its central angle is 70 what is the area of sector

To recall, a sector is a portion of a circle enclosed between its two radii and the arc adjoining them.

For example, a pizza slice is an example of a sector representing a fraction of the pizza. There are two types of sectors, minor and major sector. A minor sector is less than a semi-circle sector, whereas a major sector is a sector that is greater than a semi-circle.

In this article, you will learn:

  • What the area of a sector is.
  • How to find the area of a sector; and
  • The formula for the area of a sector.

 

What is the Area of a Sector?

The area of a sector is the region enclosed by the two radii of a circle and the arc. In simple words, the area of a sector is a fraction of the area of the circle.

Given the area of the sector of radius 6cm and its central angle is 70 what is the area of sector

How to Find the Area of a Sector?

To calculate the area of a sector, you need to know the following two parameters:

  • The length of the circle’s radius.
  • The measure of the central angle or the length of the arc. The central angle is the angle subtended by an arc of a sector at the center of a circle. The central angle can be given in degrees or radians.

With the above two parameters, finding the area of a circle is as easy as ABCD.  It is just a matter of plugging in the values in the area of the sector formula given below.

Formula for area of a sector

There are three formulas for calculating the area of a sector. Each of these formulas is applied depending on the type of information given about the sector.

Area of a sector when the central angle is given in degrees

If the angle of the sector is given in degrees, then the formula for the area of a sector is given by,

Area of a sector = (θ/360) πr2

A = (θ/360) πr2

Where θ = the central angle in degrees

Pi (π) = 3.14 and r = the radius of a sector.

Area of a sector given the central angle in radians

If the central angle is given in radians, then the formula for calculating the area of a sector is;

Area of a sector = (θr2)/2

Where θ = the measure of the central angle given in radians.

Area of a sector given the arc length

Given the length of the arc, the area of a sector is given by,

Area of a sector = rL/2

Where r = radius of the circle.

L = arc length.

Let’s work out a couple of example problems involving the area of a sector.

Example 1

Calculate the area of the sector shown below.

Given the area of the sector of radius 6cm and its central angle is 70 what is the area of sector

Solution

Area of a sector = (θ/360) πr2

= (130/360) x 3.14 x 28 x 28

= 888.97 cm2

Example 2

Calculate the area of a sector with a radius of 10 yards and an angle of 90 degrees.

Solution

Area of a sector = (θ/360) πr2

A = (90/360) x 3.14 x 10 x 10

= 78.5 sq. yards.

Example 3

Find the radius of a semi-circle with an area of 24 inches squared.

Solution

A semi-circle is the same as half a circle; therefore, the angle θ = 180 degrees.

A= (θ/360) πr2

24 = (180/360) x 3.14 x r2

24 = 1.57r2

Divide both sides by 1.57.

15.287 = r2

Find the square root of both sides.

r = 3.91

So, the radius of the semi-circle is 3.91 inches.

Example 4

Find the central angle of a sector whose radius is 56 cm and the area is 144 cm2.

Solution

A= (θ/360) πr2

144 = (θ/360) x 3.14 x 56 x 56.

144 = 27.353 θ

Divide both sides by θ.

θ = 5.26

Thus, the central angle is 5.26 degrees.

Example 5

Find the area of a sector with a radius of 8 m and a central angle of 0.52 radians.

Solution

Here, the central angle is in radians, so we have,

Area of a sector = (θr2)/2

= (0.52 x 82)/2

= 16.64 m2

Example 6

The area of a sector is 625mm2. If the sector’s radius is 18 mm, find the central angle of the sector in radians.

Solution

Area of a sector = (θr2)/2

625 = 18 x 18 x θ/2

625 = 162 θ

Divide both sides by 162.

θ = 3.86 radians.

Example 7

Find the radius of a sector whose area is 47 meters squared and central angle is 0.63 radians.

Solution

Area of a sector = (θr2)/2

47 = 0.63r2/2

Multiply both sides by 2.

94 = 0.63 r2

Divide both sides by 0.63.

r2 =149.2

r = 12.22

So, the radius of the sector is 12.22 meters.

Example 8

The length of an arc is 64 cm. Find the area of the sector formed by the arc if the circle’s radius is 13 cm.

Solution

Area of a sector = rL/2

= 64 x 13/2

= 416 cm2.

Example 9

Find the area of a sector whose arc is 8 inches and radius is 5 inches.

Solution

Area of a sector = rL/2

= 5 x 8/2

= 40/2

= 20 inches squared.

Example 10

Find the angle of a sector whose arc length is 22 cm and the area is 44 cm2.

Solution

Area of a sector = rL/2

44 = 22r/2

88 = 22r

r = 4

Hence, the radius of the sector is 4 cm.

Now calculate the central angle of the sector.

Area of a sector = (θr2)/2

44 = (θ x 4 x 4)/2

44 = 8 θ

θ =5.5 radians.

Therefore, the central angle of the sector is 5.5 radians.

 

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Solution:

We use the formula for the area of the sector of a circle.

The formula for the area of the sector of a circle with radius 'r' and angle θ = (θ/360°) × πr2

Given, θ = 60°, Radius = 6 cm

Area of the sector = (θ/360°) × πr2

= 60°/360° × 22/7 × 6 × 6

= 132/7 cm2

☛ Check: NCERT Solutions Class 10 Maths Chapter 12

Video Solution:

NCERT Solutions Class 10 Maths Chapter 12 Exercise 12.2 Question 1

Summary:

The area of a sector of a circle with radius 6 cm is 132/7 cm2 if angle of the sector is 60°.

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