This lesson plan aims to teach students about finding the sum of angles in polygons. It includes 7 activities: 1) defining polygons and reviewing triangle angles; 2) calculating sums for quadrilaterals and pentagons; 3) dividing into groups to find sums for 6-, 7-, and 8-sided polygons; 4) deriving the formula for an n-sided polygon; 5) reviewing the formula; 6) concluding; and 7) following up with example problems. The teacher uses discussion, diagrams, and grouping to help students understand how to divide polygons into triangles and add the triangle angles to find the total sum.

1. LESSON PLAN
CURRICULAR STATEMENT: To understand about sum of the angles of a
polygon through discussion , observation, organization of charts and by
analyzing the prepared notes of the pupil.
CONTENT ANALYSIS :
New terms : Sum of angles
Facts : Any polygon can be divided into a number of triangles
Concepts : Concept of sum of angles of a polygon
Process : Process of finding sum of angles of a polygon
LEARNING OUTCOMES
The pupil will be able to:-
1. recall the term sum , angles , polygons etc.
2. recognize the angles of a polygon
3. identifies the concept of sum of angles of polygons
4. explains the method of finding sum of angles of polygons
5. suggest different method of finding sum of the angles of polygons
6. detect errors while finding sum of angles of polygons
7. ask questions to know more about sum of angles of polygons
8. discuss the problems on finding sum of angles of polygons
9. reads charts quickly and accurately on sum of angles of polygons
10.does oral and written calculations with speed and accuracy
PRE-REQUISITES : The students have knowledge on sum of the angles of a
triangle
Name of the teacher : Stephy Johnson
Subject : Mathematics
Unit : Polygons
Sub unit : Sum of angles
Name of the school : St.Stephen’s HSS ,
Pathanapuram
Standard : VIII F
Strength : 38/40
Date :28/07/2015
Time : 40 minutes

2. TEACHING – LEARNING : Usual classroom aids, activity cards ,chart
RESOURCES
LEARNING STRATEGIES : Group discussion , individual work ,observation
,activity, observing charts and explanation by the teacher
Classroom interaction procedure Expected pupil responses
INTRODUCTION
ACTIVITY 1
i)What is a polygon ? Students answer correctly
ii) What is the sum of the angles of a
triangle ?
Through these questions teacher leads the
students to the concept of sum of angles.
PRESENTATION
ACTIVITY 2
i)Teacher draws the following quadrilateral
on the blackboard and draw a diagonal on it
(BB)
i)How many triangles we obtain? Students says that 2 triangles
ii)How can we calculate the sum of the angl-Students says that we can find it by
es of the quadrilateral? adding angles of the triangle.
iii)Teacher writes on the blackboard as
follows
Sum of angles of a quadrilateral= 180+180
= 2 x 180
=360 (BB)

3. Classroom interaction procedure Expected pupil responses
ACTIVITY 3
i)Teacher draws a pentagon and divide it
into triangles by fixing a vertex and join it
with other vertices using line segments as
follows
(BB)
ii)How many lines and triangles are here? Students reply as 2 lines and 3
iii)Teacher writes on the black board as triangles
follows
Sum of angles of pentagon=3 x 180
= 540 (BB)
ACTIVITY 4
i)Teacher divides the class in to groups and All groups correctly find the
distribute the activity cards containing the answer
question of finding sum of the angles of 6,7
and 8 sided polygon as above procedure
ii) Teacher calls representatives from each
group and asks them to write answer on the
blackboard
For a 6 sided polygon,3 lines and4 triangles
Sum = 4 x180 =720

4. Classroom interaction procedure Expected pupil responses
For an 7 sided polygon,4 lines and5triangles
Sum= 5 x 180 =900
For an 8 sided polygon,5 lines and6triangles
Sum= 6 x 180 =1080 (BB)
ACTIVITY 5
i)Teacher asks how many lines can be drawn Students says that there are n-3
in an n-sided polygon lines can be drawn.
ii)How many triangles are there? n-2 triangles
iii)What is the sum of angles? Students says that sum is (n-2)180
iv)Teacher shows achart containing the
following formula
The sum of the angles of an n-sided Students write the formula on their
Polygon is (n-2) 180 notebook
CLOSURE
ACTIVITY 6
Teacher concludes the class by saying the
method of finding sum of the angles of a
polygon and the formula for finding it.
REVIEW
ACTIVITY 7
Teacher asks the formula for finding sum of All students answer correctly
the angles of an n-sided polygon to the
students

5. Classroom interaction procedure Expected pupil responses
FOLLOW UP ACTIVITIES
i)Find sum of the angles of a 20 sided
polygon?
ii)Is the sum of the angles of a polygon is
2700?