# Geometry Chapter 3

Transversal

A line that intersects two or more lines in a plane at different points is called a transversal

Non-Euclidean geometry

Spherical geometry is one type of non-Euclidean geometry

if and only if

If both a conditional and its converse are true, it can be written in if and only if form

Parallel Postulate

If there is a line and a point not on the line, then there exists exactly one line through the point that is parallel to the given line.

Slope

In a coordinate plane, the slope of a line is the ratio of its vertical rise to the horizontal run.

Spherical geometry

a system of points, great circles (lines), and spheres (planes)

plane Euclidean geometry

A system of points, lines and plans

Equidistant

Equidistant means that the distance between two lines measured along a perpendicular line to the line is always the same.

alternate exterior angles, alternate interior angles, consecutive interior angles, corresponding angles, interior angle, exterior angle

See page 126 of the text

Distance between parallel lines

The distance between two parallel lines is the distance between one of the lines and any point on the other line.

Distance between a point and a line

The distance from a line to a point not on the line is the length of the segment perpendicular to the line from the point.

Skew lines

Two lines are skew if they do not intersect and are not in the same plane.

Parallel lines

Two lines in a plane that never meet are called parallel lines