1) The document provides lesson objectives, examples, and formulas for finding the area of a sector of a circle. 2) A sector is a wedge of a circle bounded by two radii and the minor arc they determine. The formula for finding the area of a sector is: Area = (central angle in degrees/360) x πr^2. 3) Examples are worked out to demonstrate finding the area of sectors using the formula. Definitions and formulas are generalized. Practice problems are provided for students.

1. TOPIC: Plane Coordinate Geometry
Subtopic: Area of a Sector of a Circle
Mathematics Grade 10

2. OBJECTIVES:
At the end of the period, at least 85% of the
students with at least 85% proficiency are
expected to:
Find the length of an arc and the area of a
sector of the circle;
Apply mathematical concepts in solving the
area of a sector of the circle;
Show active participation during class
discussion.

3. . Drill/Review
Direction: Find the area of each circle and each triangle.
15 cm
16 cm
706.5 cm 2 200.96 cm2
10 cm
8cm
40
cm2

4. . Motivation
• Direction: Using
the figure, find the
following measure.
• mBC
• m∠𝐹𝐺𝐸
• mAF
• m∠𝐴𝐺𝐵
• m∠𝐵𝐺𝐹
•
60
60
50
70
120

5. Development of the Lesson
1.Ask the students to recall the definition of
central angles and area of the circle.
We've all had a slice of pie or a piece of pizza.
Both are real life examples of a sector of a
circle. 2.A sector is a wedge of a circle made
from two radii. Radii is the plural of radius,
which is a line segment that starts on the
outside of the circle and ends at the center of
the circle. A radius is like the cut from the crust
of the pizza to the middle.

6. Area of a sector
Sometimes you are really hungry and want a slice of
pizza that is larger than your friend's slice. You can
usually look at the pizza and figure out which slice is
bigger, but there is also a mathematical way to figure
out the size. The formula for area of a sector is
based on the formula for the area of a circle, except
that you only want the area of part of the circle
instead of the whole.
Introduce sector of a circle by showing the
figure:
Formula:
A =
𝑛
360
𝜋𝑟2
; where n is the number of
degrees in the
central angle of a sector

7. Illustrative example:
sol. . Area of Sector = n/360 x

8. Generalization
A SECTOR OF A CIRCLE is a region in the
circle bounded by two radii and the minor arc
they determine.
Area of a sector = n/360 x 3.14 r2
A SEGMENT OF A CIRCLE is a region of a
circle bounded by an arc and the segment
joining its endpoints.
Area of a segment = area of a sector minus
area of the triangle formed.

9. Practice Exercises
Direction: Find the area
of the shaded sector in
each circle below.
8cm

10. Assignment
Direction: Find the area of the triangle.