# 1.2 Points, Lines, and Planes

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1.2 Points, Lines, and Planes
Chapter 1 1.2 Points, Lines, and Planes

Point A location, represented by a capital letter, has no size.

Space A set of points.

Line A series of points that extends in two opposite directions without end. A B m Named using: AB or line m

Collinear points Points that lie on the same line
B m C D Points A, B, and C are collinear Points A, C and D are noncollinear

Plane It is a flat surface that has no thickness. It contains many lines and extends without end in the directions of all of its lines. It is names either by a single capital letter, or by at least 3 noncollinear points.

Coplanar Points and lines that lie in the same plane are called this

Postulate or axiom An accepted statement of fact.

POSTULATES: 1-1: Through any two points there is exactly one line
1-2: If two lines intesect, then they intersect in exactly one point. 1-3: If two planes intersect, then they intersect in exactly one line. 1-4: Through any three noncollinear points, there is exactly one plane.

Example 1: Are the three points collinear? If so, name the line on which they lie. A, D, E ? B, C, D ? A, E, C ? Name line m in three other ways. . m A . . G n B C D F E l

Example 2 Name the plane represented by each surface of the box.
The bottom The top The front The back The right side The left side M A H D N R I T