This document provides information about calculating the interior angles of polygons. It explains that polygons can be divided into triangles by connecting alternating vertices, and the number of triangles is equal to two less than the number of sides. It then states the formula to calculate the sum of the interior angles of any polygon: the sum is equal to (n-2) x 180 degrees, where n is the number of sides. The document demonstrates this formula for triangles, quadrilaterals, pentagons and hexagons.

1. WELCOME

2. NAME OF THE TEACHER : ANEES A J
STANDARD:9
UNIT :POLYGONS
TOPIC : INTERIOR ANGLES OF POLYGON
OBJECTIVE : TO UNDERSTAND THAT THE SUM OF
INTERIOR ANGLES
A POLYGON HAVING ‘N’ SIDES =(N-2)*180

3. INTERIOR ANGLES OF A POLYGON

4. STEPS TO FIND OUT THE INTERIOR ANGLES OF POLYGONS
 Polygons can be divided into triangles by joining
alternative vertices.
 The number of triangle = Two less than the number of
sides of the original polygon.
 Since the sum of the angles of a triangle is 180, we can find
the sum of angles of polygon by multiplying the number of
triangles with 180

5. SUM OF INTERIOR ANGLES
TRIANGLE QUADRILATERAL= PENTAGON=
2 TRIANGLES 3 TRIANGLES
HEXAGON= 4 TRIANGLES HEPTAGON= 5 TRIANGLES

6. SHAPE NUMBER OF
SIDES
NUMBER OF
TRIANGLES
SUM OF THE
ANGLES
(DEGREE)
TRIANGLE 3 1=(3-2) 1*180=180
QUADRILATERAL
4 2=(4-2) 2*180=360
PENTAGON 5 3=(5-2) 3*180=540
HEXAGON 6 4=(6-2) 4*180=720

7. From the above table we can conclude that the sum of
the angles of a polygon having ‘n’ sides is (n-2)180.
As the number of sides increases the sum of angles
increases by 180 degree.

8. THANK YOU