Cone: a solid with one circular base. In a cone, the vertex is in the middle of the base.
Cylinder: a solid with two circular bases. There are oblique cylinders and right cylinders.
Sphere: a solid formed by a set of points in space, equidistant to a given center. This definition is very similar to the definition of a circle, but the only different is that a circle in on a plane while a sphere is in space.
Then we learned about platonic solids, which are solids that were discovered by Plato, that are only formed by the same regular polygons. There are only 5, it is impossible to have any other solids formed by the same regular polygons.
Tetrahedron: - it has 4 faces
- all faces are equilateral triangles
Hexahedron: - it has 6 faces
- all faces are squares
(- this is most commonly known as a cube)
Octahedron: - it has 8 faces
- all faces are equilateral triangles
Dodecahedron: - it has 12 faces
- all faces are regular pentagons
Icosahedron: - it has 20 faces
- all faces are equilateral triangles
Afterwards, we did some practice problems to find the area of a solid, which is when you find the area of the shapes that form the sides, and then add them all.
Our homework was page 588, #23, 24 and 25. This is a continuation of the exercises we were doing in class.
(:
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