​Objectives

• ​Define polygons

• ​Names of polygons

• ​Find the sum of interior and exterior angles in polygons

• ​Use the sum of interior and exterior angles to find missing angles in polygons

​Polygon

​A polygon is a two-dimensional shape made up of straight lines, and the shape is closed.

​What's in a name?

​Poly means many

​gon means angles

​

​Polygon means many angles

TYPES AND NAMES OF POLYGONS​

​Regular Polygon

A regular polygon is EQUILATERAL

and

EQUIANGULAR

​Types of Polygons

​​Draw a table in your books with two columns. We will fill in the columns from the information in the upcoming video.

​

​Number of sides Name of Polygon

INTERIOR ANGLES IN POLYGONS​

FINDING MISSING ANGLES

Solving for the missing angle!

• To solve for the missing angle follow these steps!

• 1) Count the number of sides on the polygon - here we have 5 sides (pentagon)

• 2) Use our formula for the sum of the interior angles - S = 180(n - 2) S = 180(5-2) = 540 degrees

• 3) Add up the existing angles - 87 + 105 + 135 + 92 = 419 degrees

• 4) Subtract the sum of the existing angles from the sum of the interior angles : 540 - 419 = 121 degrees

Finding n​

​Example

​The sum of the interior angles of a regular polygon is 1800.

​

​How many sides does the polygon have?

​

​Find the measure of each interior angle.

Example!