math

1. Angles
of a
Polygon

2. Objectives:
At the end of the lesson the learner will be
able to
Name the parts of a polygon and classify
them as either convex or concave
Classify polygons according to the
number of sides
Determine the sum of the measures of the
interior angles of a polygon

4. Parts of a Polygon
Four important terms related to a polygon:
Interior angle
Side
Vertex
Diagonal

7. Convex and Concave
Polygons
Polygons can be also be classified as either convex or
concave. Consider the following examples:

9. Sum of the Measures of
Interior Angles of Polygons

11. Example 2: Find the sum of the measures of interior
angles of an octagon.
Solution:
Sum of the measures of interior angles of a polygon
= (n – 2) ∙180°
Therefore, the sum of the measures of interior angles of
an octagon
= (8 – 2) ∙180°
= 6 ∙ 180°
= 1080°

12. Example 3: Find the measure of each interior
angle of a regular nonagon.

13. Example 4: The sum of the measures of
interior angles of a polygon is 1 440°. How
many sides does the polygon have?

14. Exterior Angles of a Polygon