3-Dimensional Figures

Polygons (Two dimensional)

• A polygon is a geometric figure that is made up of three or more line segments that intersect only at their endpoints.

• The number of sides determines the name of the polygon.

POLYGONS

• Triangle• 3 sides

• Quadrilateral• 4 sides

• Pentagon• 5 sides

POLYGONS

• Hexagon• 6 sides

• Heptagon• 7 sides

• Octagon• 8 sides

Regular Polygons

• A regular polygon is a polygon with all sides equal in length and all angles equal in measure.

A Regular Polygon Question

• The polygon shown is a regular pentagon. Find the perimeter of the pentagon.

3 ft

Since it’s a regular pentagon, all the sides are the same length.

5 (3 ft) = 15 ft

Another Regular Polygon

•A regular hexagon has a total perimeter of 150 inches. Find the measure of each side of the polygon.

A hexagon has 6 sides. Since it’s a regular hexagon all of the

sides are equal in length.150 ÷ 6 = 25 inches

Each side measures 25 inches.

Polygons in Real Life?Guess which polygon is in each picture.

1

2Trapezoid

Square

Polygons in Real Life?

3 4

Triangle

Heptagon

Polygons in Real Life?

5

6

Quadrilateral

Octagon

Polygons in Real Life?

7

8

Pentagon

Parallelogram

A three dimensional figure that has three dimensions: length, width, and height.

cubecylinder

cone

Rectangular prism

pyramid

Some Vocabulary

•Polyhedron: A 3-D figure whose faces are all polygons.

• Face: A flat surface of a three-dimensional figure.

•Edge: The line where two faces meet.

•Vertex: The point where three or more edges meet.

•Base: The face that is used to name a polyhedron.

Vertices (points)

Edges (lines)

Faces (planes)

10

15

7

Naming Polyhedrons

Step 1: Identify the base of the solid. It will be used to name the polyhedron.

Hint: It will be the name of a polygon.

Step 2: Determine if the object is a prism or pyramid.

Step 3: Name the polyhedron.

Naming Solids: Step 1

Identify the base of the solid. It will be used to name the polyhedron.

Hint: It will be the name of a polygon.

Example:

There is one base, and it is a pentagon.

Naming Solids: Step 2

Determine if the object is a prism or pyramid.

Naming Solids: Step 2

Example:

There is one base that is a polygon and there are five triangular faces, which makes it a pyramid.

Naming Solids: Step 3

Name the polyhedron

Example:

Base: Pentagon

Faces: Pyramid

Name: Pentagonal Pyramid

Combine what you found in Steps 1 and 2 to name the figure.

Other three-dimensional figures include cylinders, cones, and spheres. These figures are not polyhedrons because they are not made of faces that are all polygons.

Not Polyhedrons

Cylinders Cones Spheres

Naming Solids Activity• Use the list of names of the solids on the board. Work in your groups to

match the name of the solid to its picture on your worksheet.• Once you have discovered the names of each solid, work in your groups

to fill in the rest of the chart.• HINT: use your notes on steps to naming solids.

You will have 10 minutes. Make sure to watch the clock.GOOD LUCK!