POLYGONSBrought to you by powerpointpros.com…

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1. What is a Polygon?

2. Naming Polygons

3. Regular/ Irregular Polygons

4. Concave/ Convex Polygons

5. Polygon Practice

PLAY ALLNOTE: Each section, when played by itself, will include a practice

problem from the Polygon Practice section. If “Play All” is selected, practice problems will be saved for the end.

WHAT IS A POLYGON?Section 1

Characteristics of PolygonsA polygon must meet all 4 of these

requirements:

1. A polygon must be a closed figure.

2. A polygon must be composed of 3 or more line segments.

3. A polygon must only have straight sides.

4. All lines of a polygon intersect only at vertices.

1. A polygon must be a closed figure.

What this statement means is that a polygon must not have any openings or breaks in the lines. Think of it like a fence. A polygon is like a fence that can’t have any gates or holes in it.

POLYGONNOT A POLYGON

2. A polygon must be composed of 3 or more line segments.

This statement says that a shape must have 3 or more sides to be considered a polygon.

POLYGONNOT A POLYGON

REMEMBERING SKILLSThis shape isn’t a polygon because it has

only one “side.” Why else isn’t it a polygon?

3. A polygon must only have straight sides.

This requirement states that any shape that has a curved side isn’t a polygon, since a polygon’s sides must be straight.

POLYGON

NOT A POLYGON

4. All lines of a polygon intersect only at vertices.

Key Word: vertices (vertex, singular)

The “corners” of a polygon, the point where sides end.

This requirement states that a polygon’s sides can’t cross each other; sides that intersect must end at that intersecting point.

POLYGONNOT A POLYGON

Review

1. A polygon must be a closed figure.

2. A polygon must be composed of 3 or more line segments.

3. A polygon must only have straight sides.

4. All lines of a polygon intersect only at vertices.

NAMING POLYGONSSection 2

How to Name a Polygon

Polygons can be named by the number of sides that they have. In this presentation, we include the names of polygons with 3-10 sides, but there are names for polygons with more than 10 sides (but not less than 3, remember!)

Basic Names for Polygons Teacher Note

This very same document is available for you to print out for

your students at www.powerpointpros.com. It is listed as an additional resource under the Polygons PowerPoint

post.

Other Names for PolygonsThere are other names for polygons as

well, such as regular, irregular, concave, and convex. You can learn about those in the coming sections.

REGULAR/ IRREGULAR POLYGONS

Section 3

Regular Polygons

Key Word: regular polygon A polygon with congruent sides and angles.

A regular polygon has congruent sides and angles. This means that all the sides should be exactly the same length, and all angles should measure the same number of degrees. REGULAR DECAGON

Irregular Polygons

Key Word: irregular polygon A polygon that doesn’t have congruent sides and/or angles.

An irregular polygon is, basically, the exact opposite of a regular polygon.

IRREGULAR HEPTAGON

CONCAVE/ CONVEX POLYGONS

Section 4

Convex Polygons

Key Word: convex polygon A polygon in which all diagonals from vertices are in the interior of the polygon.

A convex polygon is a polygon where if you draw diagonal lines from any vertex to any other vertex, it will be in the interior of the polygon.

Let’s demonstrate, shall we?

This is a convex hexagon. Here’s why:

No matter how many times we “connect the vertices”, all the lines are in the interior of the hexagon.

Concave Polygons

Key Word: concave polygon A polygon in which all diagonals from vertices are NOT in the interior of the polygon.

A concave polygon is basically the exact opposite of a convex polygon.

Let’s demonstrate, shall we?

This is a concave hexagon. Here’s why:

STOP RIGHT THERE

…

This is a concave hexagon because when we connected two vertices together, the line went outside the hexagon.

POLYGON PRACTICESection 5

Practice

State why each shape isn’t a polygon.

Practice

State why each shape isn’t a polygon.

It isn’t a closed figure.

Why?

Practice

State why each shape isn’t a polygon.

It isn’t a closed figure, and it

isn’t made up of 3 or more sides.

Why?

Practice

State why each shape isn’t a polygon.

It is round.

Why?

Practice

State why each shape isn’t a polygon.

Its lines intersect at

a place other than a vertex (corner).

Why?

Practice Name each polygon by the number of sides it has.

Practice Name each polygon by the number of sides it has.

This polygon is a…

quadrilateral

Practice Name each polygon by the number of sides it has.

This polygon is a…

heptagon

Practice Name each polygon by the number of sides it has.

This polygon is a…

triangle

Practice Name each polygon by the number of sides it has.

This polygon is a…

decagon

Practice Name each polygon by the number of sides it has.

This polygon is a…

hexagon

Practice

Name each polygon as regular or irregular.

Practice

Name each polygon as regular or irregular.

This polygon is a(n)…

polygon.

regular

Practice

Name each polygon as regular or irregular.

This polygon is a(n)…

polygon.

regular

Practice

Name each polygon as regular or irregular.

This polygon is a(n)…

polygon.

irregular

Practice

Name each polygon as regular or irregular.

This polygon is a(n)…

polygon.

irregular

Practice

Name each polygon as regular or irregular.

This polygon is a(n)…

polygon.

regular

Practice

Name each polygon as concave or convex.

Practice

Name each polygon as concave or convex.

This polygon is a(n)…

polygon.

concave

Practice

Name each polygon as concave or convex.

This polygon is a(n)…

polygon.

convex

Practice

Name each polygon as concave or convex.

This polygon is a(n)…

polygon.

convex

Practice

Name each polygon as concave or convex.

This polygon is a(n)…

polygon.

concave

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