Page 49 - Math Course 2 (Book 2)

Polygons

Let’s Begin MO. 8 - L3b
Measures of the Interior and

Exterior Angles
Classify Polygons

Example Key Concept

Interior Angles of a Polygon
A. Classify the polygon.

This polygon has 5 sides. If a polygon has n sides, then n – 2 triangles are
formed. The sum of the degree measures of the
interior angles of the polygon is (n – 2) 180.

Answer It is a pentagon.

Let’s Begin

B. Classify the polygon.
This polygon has 7 sides.
Measures of Interior Angles

Example
Answer It is a heptagon.

Find the sum of the measures of the interior
angles of a quadrilateral.

Your Turn! A quadrilateral has 4 sides. Therefore, n = 4.

(n – 2)180 = (4 – 2)180 Replace n with 4.
Classify Polygons
= 2(180) or 360 Simplify.
A. Classify the polygon.

A. pentagon The sum of the measures of
B. hexagon Answer the interior angles of a
C. heptagon quadrilateral is 360°.
D. octagon

Answer Real World Example

TRAFFIC SIGNS
B. Classify the polygon.
A stop sign is a regular octagon. What is the
A. nonagon measure of one interior angle in a stop sign?
B. octagon
C. heptagon Step 1 Find the sum of the measures of the
D. hexagon angles. An octagon has 8 sides.
Therefore, n = 8.
Answer (n – 2)180 = (8 – 2)180 Replace n with 8

= 6(180) or 1080 Simplify.

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