Trigonometry For Dummies
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A polyhedron is the three-dimensional equivalent of a polygon, which is a shape that has only straight sides. Similarly, a polyhedron is a solid that has only straight edges and flat faces (that is, faces that are polygons).


The most common polyhedron is the cube. As you can see, a cube has 6 flat faces that are polygons — in this case, all of the faces are square — and 12 straight edges. Additionally, a cube has 8 vertexes (corners).


The above figure shows a few common polyhedrons.


The above figure shows a special set of polyhedrons called the five regular solids. Each regular solid has identical faces that are regular polygons. Notice that a cube is a type of regular solid. Similarly, the tetrahedron is a pyramid with four faces that are equilateral triangles.

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Mary Jane Sterling taught algebra, business calculus, geometry, and finite mathematics at Bradley University in Peoria, Illinois, for more than 30 years. She is the author of several For Dummies books, including Algebra Workbook For Dummies, Algebra II For Dummies, and Algebra II Workbook For Dummies.

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