2. The line segment between two points is the shortest.

3. The complementary angles of the same angle or equal angle are equal.

4. The complementary angles of the same angle or equal angle are equal.

5. There is one and only one straight line perpendicular to the known straight line.

6. Of all the line segments connecting a point outside the straight line with points on the straight line, the vertical line segment is the shortest.

7. The axiom of parallelism passes through a point outside a straight line, and one and only one straight line is parallel to this straight line.

8. If two straight lines are parallel to the third straight line, the two straight lines are also parallel to each other.

9. The same angle is equal and two straight lines are parallel.

10. The internal dislocation angles are equal and the two straight lines are parallel.

1 1. The inner angles on the same side are complementary and the two straight lines are parallel.

12. Two straight lines are parallel with the same included angle.

13. Two straight lines are parallel and the internal dislocation angles are equal.