Eligible Content M3.C.1.1.1

Eligible Content M3.C.1.1.1

Help Me To:

Name/identify/describe geometric shapes in two dimensions (circle, square,
rectangle, triangle, pentagon and octagon).

Did You Know?

All polygons are closed figures, but not all closed figures are polygons.
Look further in the lesson to find out why?

Look at the examples below. These figures are polygons.

Look at the examples below. These figures are NOT polygons.

Check What You Know First on Customary Units

Answer these questions with true or false.

A rectangle is a polygon.

A circle is a polygon.

A polygon with three sides and three angles is an octagon.

A polygon with five sides and five angles is a pentagon.

Key Vocabulary

whole

A plane figure is a closed figure that lies on a flat surface and is all in one plane.

A closed figure is a shape that begins and ends at the same point.

A polygon is a closed figure with straight sides; each side is a line segment.
Polygons are named by the number of sides and angles they have.

The side is each line segment of a polygon.

Learn About It Now

Plane figure are two-dimensional. They can lie on a flat surface. Circles, squares,
rectangles, triangles, pentagons and octagons are examples of plane figures.

Polygons are closed figures made up of 3 or more straight lines.
Squares, rectangles, triangles, pentagons and octagons are
examples of polygons because they are closed figures with 3 or
more straight lines.

A circle would not be a polygon because it is not made up of 3 or
more straight lines and has no angles.

An open figure is not a polygon because a polygon must be a closed figure.

Polygons are named by the number of sides and angles they have. For example, quadrilaterals
are polygons with four sides and four angles. They include squares, rectangles, parallelograms
and rhombuses.

Look at the following polygons and the number of sides and angles for each.

The following chart names some additional polygons and the number of sides and angles for each.

Name	Sides	Angles
Triangle	3	3
Quadrilateral	4	4
Pentagon	5	5
Hexagon	6	6
Heptagon	7	7
Octagon	8	8
Nonagon	9	9
Decagon	10	10

Refer to following chart for the definitions of the various shapes.

Definitions of Two-Dimensional Shapes

Two-dimensional shapes are flat. Read about properties of these two-dimensional shapes.
Triangle	A triangle is a two-dimensional shape with three straight sides and three angles. There are different types of triangle called equilateral, isosceles, scalene and right-angled.
Square	A square is a special rectangle that has four sides of the same length and four angles of 90 degrees. It has two pairs of opposite sides that are parallel.
Rectangle	A rectangle is a four-sided shape with two pairs of parallel sides that meet at right-angles. It has two long sides and two shorter sides. A square is a special kind of rectangle because all its sides are the same length.
Circle	A circle is a round, flat two-dimensional shape where all points on the circumference are the same distance from the center.
Hexagon	A hexagon is a two-dimensional shape with six straight sides and six angles. In a regular hexagon all the sides are the same length and the angles are the same.
Pentagon	A pentagon is a two-dimensional shape with five straight sides and five angles. A regular pentagon has all its sides the same length and all its angles equal.
Octagon	An octagon is a flat shape with eight equal sides and eight equal angles.
Remember that shapes can have line symmetry and rotational symmetry.

More Practice on Two-Dimensional Geometric Shapes

Click below to review what you have learned about polygons and then take a quiz.
The program is entitled Pete’s Polygons.
www.beaconlearningcenter.com/WebLessons/

Now that you have reviewed the basic shapes and polygons,
Click below to take the following quizzes on types of polygons and the
number of sides and angles of each one.

Types of Polygons
http://www.aaamath.com/geo318-polygons-numbers.html

Polygons II
http://www.321know.com/geo318x1.htm

Websites to Check Out For Extra Practice

Click below to learn more about polygons and solid figures.
http://eduplace.com/math/mhm/3/07/index.html

Click below to play a challenge game for two players for basic geometry vocabulary, triangles,
quadrilaterals, and polygons.
http://www.quia.com/cb/12366.html

Click below to play several games on geometry terms which include Flash Cards, Matching,
Concentration and Word Search.
http://www.quia.com/jg/65535.html

Click below to play a flashcard game on Geometric Shapes. There are also flashcard
games for other math skills as well.
http://www.aplusmath.com/Flashcards/index.html

Click below to review geometry vocabulary matched with a drawing of the geometric figure.
Also try the following geometry activities:
Geometry Math-O
Geometry Hidden Picture
Geometry Flashcard
Geometry Terms Games
Geometry Crossword
Lines, Rays & Angles Quiz
http://www.mrsdell.org/geometry/vocabulary.html