Basic Geometry Unit

10.6 – Polygons

Polygons

A polygon is a simple, closed figure in a plane that is formed by three or more sides. The sides meet only at the vertices.

Frequently Used Types of Polygons:

Triangle3 sides

Quadrilateral4 sides

Pentagon5 sides

Hexagon6 sides

Octagon8 sides

Decagon10 sides

Less Frequently Used Polygons

7 sides – Heptagon9 sides – Nonagon12 sides - Dodecagon

Diagonals & Regular Polygons

A diagonal is a line segment that joins two nonconsecutive vertices.

A regular polygon is a polygon that is equilateral (all sides congruent) and equiangular (all angles congruent.)

Sums of Interior Angles of Polygons

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

Shape Sides Angle Sum

Triangle

Quad-rilateral

Pentagon

Hexagon

“n” - gon

1. A dodecagon is a polygon with 12 sides. Find the sum of the measures of the angles of a dodecagon by using the formula.

2. A stop sign is an octagon. For your model railroad village, you use miniature stop signs. What is the measure of each angle of the stop sign?

Questions?

Homework10.6 pg 529 #4-49