POLYGONS

Understanding the properties of various shapes, or figures, is going to be key

throughout Geometry. In this lesson, we will explore some of these shapes, more formerly

known as polygons.

LEARNING OBJECTIVES

First, to distinguish between convex and concave polygons.

Next, to distinguish between regular and irregular polygons.

Lastly, to classify polygons according to how many sides they have.

WHAT ARE POLYGONS?

Closed shapes or figures in a plane with three or more sides. Alternatively, a polygon can be

defined as a closed planar figure that is the union of a finite number of linesegments. The

term polygon is derived from a Greek word meaning “many-angled”.

CONVEX VS. CONCAVE POLYGONS

Convex polygon- A polygon for which any two interior points can be connected by a line

segment that stays entirely inside the polygon.

Concave polygon- A polygon that is not convex. A line segment connecting two points may

pass outside the figure.

REGULAR VS. IRREGULAR POLYGONS

A regular polygon is a polygon in which all the angles and sides are equal.

An irregular polygon is a polygon whose sides are not the same length or whose interior

angles do not all have the same measure.

WHAT IS A TRIANGLE?

A triangle, sometimes called a trigon, is a three-sided polygon.

WHAT IS A QUADRILATERAL?

A quadrilateral is a four-sided polygon.

WHAT IS A PENTAGON?

A pentagon is a five-sided polygon.

WHAT IS A HEXAGON?

A hexagon, also referred to as a sexagon, is a six-sided polygon.

WHAT IS A HEPTAGON?

A heptagon, also referred to as a septagon, is a seven-sided polygon.

WHAT IS A OCTAGON?

An octagon is a eight-sided polygon.

WHAT IS A NONAGON?

A nonagon is a nine-sided polygon.

WHAT IS A DECAGON?

A decagon is a ten-sided polygon.

sided polygon.