Relationship of Angles Formed by Two Parallel lines and a Transversal
Complementary Angles
Angles that add up to 90 degrees
Alternate Exterior Angles
Exterior angles found on opposite sides of the transversal. When two parallel lines are cut by a transversal the alternate exterior angles are congruent. Exs. angles 1 and 8; angles 2 and 7.
Alternate Interior Angles
Interior angles found on opposite sides of the transversal. When two parallel lines are cut by a transversal the alternate interior angles are congruent. Ex. angles 3 and 6 and 4 and 5.
Consecutive Interior Angles
The pairs of angles on one side of the transversal but inside the two lines are called Consecutive Interior Angles. Consecutive Interior Angles are Supplementary. Exs. angles 4 & 6; 3 & 5.
Transversal
a line that intersects two lines to form eight angles.
Vertical Angles
angles formed by the intersection of two lines. They are opposite each other and have congruent angle measurements. Exs. angles 1 & 4; 2 & 3; 5 & 8; 6 & 7.
Corresponding Angles
angles that hold the same position on two different lines cut by the transversal. When two parallel lines are cut by a transversal the corresponding angles are congruent. Exs. angles 1 & 5; 2 & 6; 3 & 7; 4 & 8.
Parallel lines
lines in the same plane that DO NOT intersect.
Supplementary Angles
two angles whose sum is 180 degrees. Exs. angles 1 & 2; 3 & 4; 5 & 6, 7 & 8, 3 & 1; 4 & 2; 7 & 5; 8 & 6.
