Given a convex polygon Rcontained in a plan , and a point V (vertex) out of we call pyramid the set of all segments .
Given the following pyramid, we have the following elements:
base: the convex polygon R.
base edges: the sides of the polygon.
side edges: the segments .
side faces: the triangles VAB, VBC, VCD, VDE, VEA.
height: distance H of the point V to the plan.
A pyramid is straight when the orthogonal projection of the vertex coincides with the center of the base polygon. Every straight pyramid whose base polygon is regular receives the name of regular pyramid. It can be triangular, quadrangular, pentagonal, etc., as its base is respectively a triangle, a quadrangle, a pentagon, etc. Look:
1st) Every triangular pyramid is named after the tetrahedron. When the tetrahedron has equilateral triangles as faces, it is called regular (all faces and all edges are congruent).
2nd) The base-based assembly of two regular square-base pyramids results in an octahedron. When the faces of the pyramids are equilateral triangles, the octahedron is regular.
Next: Parallel Section to the Base of a Pyramid