1. An inequality group consisting of several linear inequalities with the same unknowns is called a linear inequality group. The common part of the solution set of all inequalities in an inequality group is called the solution set of this inequality group. The process of finding the solution set of inequality group is called solving inequality group.

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 parallel axiom passes through a point outside the straight line, and there is only one straight line 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, internal dislocation angles are equal, and 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.

14. Two straight lines are parallel and complementary.

15. The sum of two sides of a triangle is greater than the third side.

16. The difference between two sides of a triangle is smaller than the third side.

17. The sum of the three internal angles of a triangle is equal to 180.

18. The two acute angles of a right triangle are complementary.

19. The outer angle of a triangle is equal to the sum of two non-adjacent inner angles.

20. The outer angle of a triangle is greater than any inner angle that is not adjacent to it.

2 1. congruent triangles has equal sides and angles.

22. Two triangles with two sides and their included angles equal.

23. Two triangles have two angles and their sides are congruent.

24. Two triangles with two angles and opposite sides of one angle are congruent.

25. Two triangles with three corresponding equilateral sides are congruent.

26. Two right-angled triangles with hypotenuse and a right-angled side are congruent.

27. The distance from the point on the bisector of an angle to both sides of the angle is equal.