Intro to Polyhedrons

​Polygons

• The word polygon means “many angles.” ​Poly = many; gon = angle

• ​They are 2-dimensional shapes.

• ​The sides are straight lines.

• ​Non of the line segments can cross one another

• ​The shape is “closed,” that is, all the lines are connected

Regular Polygons

Equal sides and equal angles

Any polygon that is not regular (uneven sides)

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Irregular Polygon

Multiple Choice

What is a polygon?

• A closed figure made up of straight line segments
• An open figure made up of straight line segments
• A closed figure made up of curved edges
• An closed figure made up of crossed line segments

Multiple Select

Which one is not a polygon?

Multiple Choice

Which one is a polygon?

Multiple Choice

A polygon is regular if....

• All angles are equal and all sides are equal

• Only all sides are equal

• Only all angles are equal

• All sides have different measurements

Multiple Choice

Name this polygon.

• hexagon

• pentagon

• trapezoid

• octagon

Multiple Choice

Name this polygon.

• quadrilateral

• triangle

• hexagon

• heptagon

Polyhedrons and Nets

Building blocks

​A single point is just a point.

​

We can use two points to create a line.

​

​We can use lines to create a square

​

​We can use squares to create a cube.

What is a "dimension"?

A dimension is a direction we can measure in such as ...

​

​How tall is it?

​

​How wide is it?

​

​How thick is it?

What about 2-dimensions and 3-dimensions?

A 2-dimensional object can be measured in two directions

​(height and width).

​

​A 3-dimensional object can be measured in three directions (height, width, depth).

For this lesson, we are going to look at 2-dimensional shapes ...

9.1 Polyhedrons

A polyhedron is a 3D figure that is formed by polygons.

Examples of polyhedrons include a cube, prism, or pyramid. Non-polyhedrons are cones, spheres, and cylinders because they have sides that are not polygons.

Multiple Choice

Which two figures are NOT polyhedra?

• A and B

• B and C

• D and A

• C and E

Prisms vs. Pyramids

A prism is a polyhedron with two congruent bases and the lateral sides are rectangles.

A pyramid is a polyhedron with one base and all the lateral sides meet at a common vertex.

Note: All prisms and pyramids are named by their bases.

Multiple Choice

The 3D figures shown are…

• prisms

• pyramids

Multiple Choice

The 3D figures shown are…

• prisms

• pyramids

9.2 Nets of 3D Shapes

A net is an unfolded, flat representation of the sides of a 3D shape.

Note: There are several different nets of any polyhedron.

Multiple Choice

A flat "unfolded" representation of a prism or pyramid.

• Surface Area

• Net

• Base

• 3-Dimensional

Multiple Choice

Which of the following is the net of a CONE?

Multiple Choice

Which figure will this net make?

• Rectangular Prism 
• Triangular Prism
• Triangular Pyramid 
• Cube

Multiple Choice

Which figure will this net make?

• Rectangular Prism 
• Triangular Prism
• Triangular Pyramid 
• Cube

Multiple Choice

Which figure will this net make?

• Cone
• Triangular Prism
• Square Pyramid 
• Cube

Multiple Choice

Which figure will this net make?

• Hexagonal Prism
• Triangular Prism
• Octagonal Prism
• Cone

Multiple Choice

Which figure will this net make?

• Cube
• Hexagonal Pyramid
• Octagonal Pyramid 
• Cone

Multiple Choice

Which figure will this net make?

• Triangular Pyramid
• Hexagonal Pyramid
• Octagonal Pyramid 
• Cube

Multiple Choice

Which net will make square pyramid?

• Net A

• Net B

Multiple Choice

The sum of all the areas of the faces of a figure.

• Net

• Base

• Area

• Surface Area