For any two lines in the same plane, one of two relationships can occur: the lines will run parallel to each other, or they will intersect.

Lines m and l are parallel lines. They will travel to infinity in either direction and never intersect.

Lines x and y are intersecting lines. Lines can only intersect at one point and only one point.


When two lines intersect and form right angles, they are called perpendicular lines. Lines s and t are perpendicular lines.

Vertical Angles

When two parallel lines are cut by another line (a transversal) angles of equal measure are created.
The measures of
L2 =L3,
the measure of
Angles 2 and 3 are called
alternate interior
Angles 1 and 4 are called
alternate exterior




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