164 Part 3: The Shape of the World
The Least You Need to Know
- Midpoints and bisectors divide segments into two congruent segments; angle
bisectors divide angles into two congruent angles. - Angles less than 90r are acute, angles greater than 90r are obtuse. Right angles
are 90r and straight angles are 180r. - Complementary angles are two angles that add to 90r, and supplementary angles
are two angles that add to 180r. - Vertical angles are congruent; linear pairs are supplementary.
- Parallel lines never intersect; perpendicular lines intersect at right angles.
- If parallel lines are cut by a transversal, pairs of corresponding angles, alternate
interior angles, or alternate exterior angles are congruent.