Polygons

Transcript Polygons

Lesson 1-6: Classify Polygons

Polygon

   A polygon is a closed figure with the following properties It is formed by three or more line segments called sides Each side intersects exactly two sides

Examples of Polygons

A Z J B C Non-examples of polygons: C B D A E F G H Y K L X L W M H I O N M K L

Concave or Convex

 Polygons can be concave or convex.

Concave Convex

Polygons can be classified by the number of sides they have.

On page 43 of your text book

# of sides 3 4 5 6 7 8 9 10 12 n Polygon Triangle Quadrilateral Pentagon Hexagon Heptagon Octagon Nonagon Decagon Dodecagon N-gon

 In an

equilateral

polygon all sides are congruent.

 In a

equiangular

polygon all angles are congruent.

Regular Polygons

 A convex polygon in which all sides are congruent and all angles are congruent is called a regular polygon.

Think about it… Can you tell me another name for a regular triangle? Regular quadrilateral??

Example #1

 Name each polygon by the number of sides. Then classify it as convex or concave. a) b)

Example #2

 Name each polygon by the number of sides, classify it as convex or concave, and classify it as equilateral, equiangular, regular.

a) b)

Tell whether the statement is always, sometimes, or never true.

 A regular pentagon is concave.

 A pentagon is regular  A square is a regular polygon  A triangle is equilateral but not equiangular.

Draw a figure that fits the description

 A triangle that is not regular  A convex hexagon  An equiangular octagon that is not equiangular

Each figure is a regular polygon. Expressions are given for two side lengths. Find the value of x.

x + 7 -7x - 8 2x - 3 5x - 32