Answering your questions one at a time.1 - What is a platonic solid?A platonic solid is one with all faces congruent polygons, meaning that they all have the same number of sides, vertices and angle size.2 - How many are there?There are only and exactly five.3 - What are their names?TetrahedronCube (but when talking about Platonic solids, it is commonly referred to as a "hexahedron").OctahedronDodecahedronIcosahedronNote: These individual platonic solids can be identified by their unique Schlafli Symbol. This is demonstrated through the following:{p,q}p = Number of vertices at each faceq = Number of faces at each vertexSo for a dodecahedron, the Shlafli Symbol would be {5,3}, because a pentagon has five {5, or p} vertices, and at any individual vertex three {3, or q} faces meet.Understand? Great!
A polyhedron is a solid with flat faces - a cube is just one of many different examples of regular polyhedra - otherwise known as platonic solids.
Because 6 platonic solids would be too many, and 4 wouldn't be enough
A Platonic solid is the 3-D shape equivalent of a polygon: it is a three dimensional figure whose sides are congruent, regular polygons, with identical vertices. Unlike the 2-dimensional case (in which there are infinitely many polygons) there are only 5 Platonic solids: * The tetrahedron, which has 4 triangular sides. * The cube (or hexahedron), which has 6 square sides. * The octahedron, which has 8 triangular sides. * The dodecahedron, which has 12 pentagonal sides. * The icosahedron, which has 20 triangular sides. Here is how the 5 Platonic solids were found, and how we know there aren't any more: Think about the sum of the angles at a vertex (by the definition of a Platonic solid, all vertices are identical). In the plane, angles around a vertex add up to 360 degrees, but we don't want the vertex to lie flat - otherwise, we'd end up with a huge flat sheet instead of a polyhedron. We also want at least 3 polygons around a vertex, because otherwise the result will become a flat figure without volume. If the sides are triangles, we can have 3 triangles around a vertex (getting the tetrahedron), 4 triangles around a vertex (getting the octahedron), or 5 triangles around a vertex (getting the icosahedron). We can't have 6 or more, because then the sum of angles wouldn't be less than 360. If the sides are squares, we can have 3 squares around a vertex, getting the cube. 4 squares around a vertex would mean the sum of angles is 360, and 5 or more is even more impossible. Finally, we can take 3 pentagons around a vertex, getting the dodecahedron; more pentagons will give us an angle sum of over 360. We can't use any shapes with more than 6 sides, because their angles are larger and we can't even fit 3 around a vertex. Even 3 hexagons will give an angle sum of 360 degrees, and anything more than that is even worse.
It has seven names
Answering your questions one at a time.1 - What is a platonic solid?A platonic solid is one with all faces congruent polygons, meaning that they all have the same number of sides, vertices and angle size.2 - How many are there?There are only and exactly five.3 - What are their names?TetrahedronCube (but when talking about Platonic solids, it is commonly referred to as a "hexahedron").OctahedronDodecahedronIcosahedronNote: These individual platonic solids can be identified by their unique Schlafli Symbol. This is demonstrated through the following:{p,q}p = Number of vertices at each faceq = Number of faces at each vertexSo for a dodecahedron, the Shlafli Symbol would be {5,3}, because a pentagon has five {5, or p} vertices, and at any individual vertex three {3, or q} faces meet.Understand? Great!
There (not their) are 5 platonic solids.
There are different numbers on the different platonic solids.
The quick answer: because of the high degree of symmetry inherent in the Platonic solids. They are vertex-uniform, edge-uniform and face-uniform. If you hold several models of the same shape up by any vertex, all the models will appear the same. The same goes for holding the models up by any edge, or by any face. Read the following for a little more detail. Many solids that are not Platonic have symmetry as well, but the Platonic solids have some special symmetrical properties. You can create what are called 'dual polyhedrons' for solids, but the duals for Platonic solids are unique. You can form a Platonic solid's dual polyhedron by making the midpoint of every face of the original Platonic solid a vertex of the dual solid within the original. If you start with a cube, a hexahedron really, and make a new solid within it having vertexes at the centers of the square faces of the cube, the solid within will be an octahedron. Tetrahedrons are self-dual, squares and octahedrons are dual with one another, and dodecahedrons and icosahedrons are dual with one another. The dual polyhedron of a Platonic solid is always another Platonic solid. This is difficult to visualize without aid. See link for some clarification. On the dual relationship of a cube [6 faces, 8 vertexes] and octahedron [8 faces, 6 vertexes] breaking down the numbers of faces and vertexes might help. Each of the 6 faces of a cube contains one of the vertexes of the octahedron, and each of the vertexes of a cube will be at the center of one of the faces of the octahedron.
A polyhedron is a solid with flat faces - a cube is just one of many different examples of regular polyhedra - otherwise known as platonic solids.
Because 6 platonic solids would be too many, and 4 wouldn't be enough
Because 6 platonic solids would be too many, and 4 wouldn't be enough
A rectangular pyramid has five faces. Sides are the same things as faces. A pyramid with a triangular base has 4 faces. This is the more common type of pyramid in mathematics, as it is a platonic solid.
There are many possible answers: Any one of the four larger Platonic solids (not the tetrahedron). In all cases, moving one of the faces laterally will still leave a solid which will beet the requirements : the cube (hexahedron) could become a rhombohedron. There are many more shapes with fewer symmetries.
There are five Platonic solids: Tetrahedron (or triangular pyramid): 4 triangular faces Cube: 6 square faces Octahedron: 8 triangular faces Dodecahedron: 12 pentagonal faces Icosahedron: 20 triangular faces. Although not a Platonic solid, some people consider a sphere to be a regular 3d shape.
In geometry, an octahedron (plural: octahedra) is a polyhedron with eight faces. A regular octahedron is a Platonic solid composed of eight equilateral triangles, four of which meet at each vertex.It is a 3-dimensional cross polytope (shape).---Wikipedia
Solids have a defined shape and volume. Some examples include ice, wood, metal, and plastic.