#### Chapter 10 Definitions

face of a polyhedron

A flat surface of the polyhedron.

edge of a three-dimensional figure

A segment that is the intersection of two faces of the figure.

vertex of a polygon

The intersection of two sides of a polygon.

prism

A polyhedron formed by two parallel congruent polygonal bases connected by lateral faces that are parallelograms.

cylinder

A three-dimensional figure with two parallel congruent circular bases and a curved lateral surface that connects the bases.

pyramid

A polyhedron formed by a polygonal base and triangular lateral faces that meet at a common vertex.

cone

A three-dimensional figure with a circular base and a curved lateral surface that connects the base to a point called the vertex.

cube

A prism with six square faces.

net

A diagram of the faces of a three-dimensional figure arranged in such a way that the diagram can be folded to form the three-dimensional figure.

cross section

The intersection of a three-dimensional figure and a plane.

orthographic drawing

A drawing that shows a three-dimensional object in which the line of sight for each view is perpendicular to the plane of the picture.

isometric drawing

A way of drawing three-dimensional figures using isometric dot paper, which has equally spaced dots in a repeating triangular pattern.

perspective drawing

A drawing in which nonvertical lines meet at a point called a vanishing point. Perspective drawings can have one or two vanishing points.

vanishing point

In a perspective drawing, a point on the horizon where parallel lines appear to meet.

horizon

The horizontal line in a perspective drawing that contains the vanishing point(s).

polyhedron

A closed three-dimensional figure formed by three or more segments such that each segment intersects only at teir endpoints and no two segments with a common endpoint are collinear.

space

The set of all points in three dimensions.

lateral face

A face of a prism or pyramid that is not a base.

lateral edge

An edge of a prism or pyramid that is not an edge of a base.

right prism

A prism whose lateral faces are all rectangles.

oblique prism

A prism that has at least one nonrectangular lateral face.

altitude of a cylinder

A segment with its endpoints on the planes of the bases that is perpendicular to the planes of the bases.

surface area

The total area of all faces and curved surfaces of a three-dimensional figure.

lateral surface

The curved surface of a cylinder or cone.

axis of a cylinder

The segment with endpoints at the centers of the two bases.

right cylinder

A cylinder whose axis is perpendicular to its bases.

oblique cylinder

A cylinder whose axis is not perpendicular to the bases.

vertex of a pyramid

The point opposite the base of the pyramid.

regular pyramid

A pyramid whose base is a regular polygon and whose lateral faces are congruent isosceles triangles.

slant height of a regular pyramid

The distance from the vertex of a regular pyramid to the midpoint of an edge of the base.

altitude of a pyramid

A segment from the vertex to the plane if the base that is perpendicular to the plane of the base.

vertex of a cone

The point opposite the base of the cone.

axis of a cone

The segment with endpoints at the vertex and the center of the base.

right cone

A cone whose axis is perpendicular to the base.

oblique cone

A cone whose axis is not perpendicular to the base.

slant height of a right cone

The distance from the vertex of a right cone to a point on the edge of the base.

altitude of a cone

A segment from the vertex to the plane of the base that is perpendicular to the plane of the base.

volume

The number of nonoverlapping unit cubes of a given size that will exactly fill the interior of a three-dimensional figure.

sphere

The set of points in space that are a fixed distance from a given point called the center of the sphere.

center of a sphere

The point inside a sphere that is the same distance from every point on the sphere.

A segment whose endpoints are the center of a sphere and any point on the sphere; the distance from the center of a spherer to any point on the sphere.

hemisphere

Half of a sphere.

great circle

A circle on a sphere that divides the sphere into two hemispheres.

altitude of a prism

A segment with its endpoints on the planes of the bases that is perpendicular to the planes of the bases.