Mathematic Skills

1. Determine - area of sector radius - the radius - the angle subtended center of a circle

2. Find the area of segment of circle

Prior Knowledge

The students already learnt - how to convert measurement in radians to degrees and vice versa. - how to determine the length of arc, radius and angle subtended at the centre of a circle. - how to find the perimeter of the segment of circle.

Learning Outcomes:

At the end of this lesson, students will be able to:- find the area of sector radius, the radius and the angle subtended center of a circle.- answer the quiz 100% correctly.- answer at least 3 out of 5 questions given in the worksheet correctly.

CONNECT TO LESSON PLAN

Area of Sector

Area

Radius

Angle

Worksheets

Quiz

What is Area Sector of circle???

Like that???

This is a circle with center O.

And this is a circle with sector AOB.

The area shaded blue color names as

Area AOB.

O

rad

A

B

O

r cm

21

2A r

A=Area Shaded

r = radius

Angle

A

r=4 cm

270o

O

1. Diagram below shows a circle with 4cm radius and angle 270 o, find the shaded area.

Given r=4cm, angle = 270 o

270180

oo

x

4.712rad

21

2A r

21(4) 4.7122

237.696A cm

6cm

13.5cm2

OB

A

2. Find the angle of the sector AOB in radiant.

= 270o x

21

2A r

2113.5 (6)

2

13.5 18

0.75rad

BO

A

3. Diagram above shows a sector AOB with center O made from wire length 90cm, the length of arc OAB is 50cm, find : -

(a) the angle in radiant(b)The area of sector AOB

= 270o x

Given r = r cm

Perimeter = 90cm

Arc AB + OA + AB = 90cm

50 + r + r = 90cm

2r = 40

r = 40

2.5rad

s r2.5rad

4. A circle sector with area 25.2cm2 and the angle at the centre is 1.4rad. Find the radius of the circle.

21

2A r

2125.2 (1.4)

2r

236 r

6r cm

5. Find the area of minor sector AOB.

215 1.4

2

17.5cm

21

2A r

?A

5r cm

= 270o x

21

2A r

21(5) (1.4)2

A

217.5A cm