Space and Shape Unit Grade 9 Math

Platonic solids E4 Make and apply generalizations about the properties of platonic solids

To prepare for this lesson What is a polygon? What are some polygons you know? What is a regular polygon? To prepare for this lesson

Platonic solids activity #1 In our class we have 2 platonic solids We are going to begin the lesson by making platonic solids We will then try and find what is the same about all of them Platonic solids activity #1

Activity #1 Each person will cut out and assemble a 3 D platonic solid You will work in groups of 5 to compare the 5 different solids that have been made When your group has the 5 solids made go to the next slide and start to answer the questions Activity #1

Activity #1 Complete the table to the right with your group There are 5 platonic solids: Tetrahedron: Has 4 faces Hexahedron: Has 6 faces Octahedron: Has 8 faces Dodecahedron: Has 10 faces Icosahedron: Has 20 faces 1 2 3 4 5 Number of faces Number of vertices Number of edges Number of sides meeting at a vertex Activity #1

When constructing a platonic solid, what is a rule for the sides of the regular polyhedra? Why are there only 5 platonic solids/regular polyhedral? What can you say about vertices in a specific regular polyhedral? Across the platonic solids? Watch this video for both comedic and visualization purposes: https://www.youtube.com/watch?v=voUVDA gFtho Answers: Activity #1

Duality activity #2 Some platonic solids have duality After watching the video, try to create a definition of duality with your group What shapes have dulaity? https://www.youtube.com/watch?v=BsaOP5NMcCM In your groups, use sketches of 2D and 3D tetrahedrons to show that it is it’s own dual or not Duality activity #2