Angle relationships
transversal
A line that intersects two of more parallel lines
vertical angles
Opposite angles formed by two intersecting lines. Vertical angles are congruent.
linear pair
adjacent angles formed by intersecting lines; they are supplementary
straight angle
an angle that measures 180 degrees and forms a straight line
alternate interior angles
angles on opposite sides of the transversal and inside the parallel lines. They are congruent
alternate exterior angles
angles on opposite sides of the transversal and outside the parallel lines. They are congruent.
complementary angles
Two angles are complementary if the sum of their measures is 90 degrees
supplementary angles
Two angles are supplementary if the sum of their measures is 180 degrees.
same-side interior angles
When two lines are cut by a transversal, these angles are on the inside of the parallel lines on the same side of the transversal. They are supplementary.
same-side exterior angles
When two lines are cut by a transversal, these angles are outside the parallel lines on the same side of the transversal. They are supplementary.
corresponding angles
angles that have the same position on two different parallel lines cut by a transversal; they are congruent
adjacent angles
angles that share a vertex and a common side and do not overlap
parallel lines
lines in the same plane that never intersect or cross
perpendicular lines
lines that intersect to form right angles
exterior angle in a triangle
The angle formed by extending a side of a triangle. The exterior angle and its adjacent interior angle are supplementary. The measure of the exterior angle is equal to the sum of the other two measures in the triangle.