1. Coplanar lines that do not intersect.

2. Lines that do not intersect and are not coplanar.

3. Corresponding Angles

4. Alternate Interior Angles

5. Consecutive Interior Angles

6. Alternate Exterior Angles

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

8. If there is a line and a point not on the line, then there is exactly one line through the point perpendicular to the given line.

9. If two parallel lines are cut by a transversal, then the pairs of corresponding angles are congruent.

10. If two parallel lines are cut by a transversal, then the pairs of alternate interior angles are congruent.

11. If two parallel lines are cut by a transversal, then the pairs of alternate exterior angles are congruent.

12. If two parallel lines are cut by a transversal, then the pairs of consecutive interior angles are supplementary.

13. If two lines are cut by a transversal so that the corresponding angles are congruent, then the lines are parallel.

14. If two lines are cut by a transversal so the alternate interior angles are congruent, then the lines are parallel.

15. If two lines are cut by a transversal so the alternate exterior angles are congruent, then the lines are parallel.

16. If two lines are cut by a transversal so the consecutive interior angles are supplementary, then the lines are parallel.

17. If two lines are parallel to the same line, then they are parallel to each other.

19. In a coordinate plane, two nonvertical lines are parallel if and only if they have the same slope.

20. In a coordinate plane, two nonvertical lines are perpendicular if and only if, the product of their slopes is –1.

21. y = mx + b

22. Ax + By = C A, B, and C are integers A > 0

23. Line that is rising from left to right Slope is positive Horizontal line Slope is zero Vertical Line Slope is undefined Line that is falling from left to right Slope is negative

24. then the lines are perpendicular.

25. then they intersect to form four right angles.

26. then the angles are complementary.

27. If a transversal is perpendicular to one of two parallel lines, then it is perpendicular to the other.

28. In a plane, if two lines are perpendicular to the same line, then they are parallel to each other.