Warm - Up:

What do you know about polygons?

Write at least 2 sentences or bullet points.

Unit 9, Lesson 1

Intro to Polygons

You will be able to define a polygon and find polygon angle sums.

What is a Polygon:

A polygon is a number of coplanar line segments, each connected end to end to form a closed shape.

Names of Common Polygons:

Think Pair Share:

1) What is the sum of the angles in a triangle?

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2) What about a quadrilateral?

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3) What about a pentagon?

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4) Do you see a pattern? If so, what is the pattern?

Polygon Interior Angle Sum Theorem:

Sum of the angles in a polygon = (n - 2) · 180

Number of sides of the polygon

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Find the Interior Angle Sum of the Polygon:

White Boards: Find the Angle Sum of each Polygon

1. 2. Regular 11-gon

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White Boards: Find x

3.

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How do you find just ONE interior angle?

(n - 2) · 180

n

Divide the sum by the number of sides if the polygon is REGULAR!

Find One Interior Angle of the Regular Polygon:

White Boards: Find the Measure of One Interior Angle of Each Polygon

1. 2. Regular 14-gon

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Polygon Exterior Angle Sum Theorem

The sum of the measures of the exterior angles of a polygon, one at each vertex, is 360.

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So, to find the measure of ONE exterior angle, you must divide 360 by the number of sides if the polygon is REGULAR.

360

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Find the Measure of One Exterior Angle of the Regular Polygon:

White Boards:

1. Find y 2. Find one exterior angle

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of a regular 18-gon

KAHOOT

Challenge Problem:

Find x

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2x² + 3

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18

5x² - 8

2x - 1

10x

HOMEWORK:

WORKSHEET

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