Section 1-2Points, Lines and Planes

A Point

• A point has no dimension. –No length, no width and no

thickness. • It is named using capital printed letters.

A

A Line

• Two points determine a line.• A line is an infinite set of points that

extends in two directions without ending.• Has no width and no thickness• It is named using a single lower case

cursive letter or by two points on the

line, BA�

A B

l

Noncollinear• Points that ARE NOT on the same line.

Collinear• Points that are on the same line.

A Plane

• At least three noncollinear points determine a plane.

• A plane is an infinite amount of points that creates a flat surface

• It extends in two dimensions without ending.

M

AB

C

A Plane

• Has no thickness

• Usually pictured as a parallelogram, although it has NO edges

• It is named using a capital cursive letter or by three points in the plane

M

AB

C

Noncoplanar

• Points that lie in the same plane

Coplanar

• Points that DO NOT lie in the same plane

A Line segment

• Piece of a line• Has two endpoints• It is named using the two endpoints,

X Z

ZX

ray

• Part of a line• Extends indefinitely in one

direction. It has exactly one endpoint.

• It is named using the endpoint first,

X Z

ZX

Opposite raysX ZY

• Formed by three collinear points

• Share the same endpoint

• For example, Y is between X and Z so and are opposite rays

XY

ZY

Two or more geometric figures intersect if they have one or more points in common.

• The intersection of two lines is a point.

• The intersection of two planes is a line.