1. Same angle, two straight lines are parallel.

2. Two straight lines are parallel and have the same angle.

3. Two sides and their included angles correspond to the congruence of two triangles.

4. Two corners and their sides are congruent with each other.

5. Three sides correspond to the coincidence of two equal triangles.

6. The corresponding edges of congruent triangles are equal, and the corresponding angles are equal.

7. Equivalent replacement.

theorem

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

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

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

4. Two straight lines are parallel and complementary.

5. The sum of the internal angles of the triangle is equal to 180 degrees.

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

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

8. The three bisectors of a triangle intersect at a point, and the distance from the point to the three sides is equal.

9. The bisector of the top corner of the isosceles triangle, the median line on the bottom edge and the height on the bottom edge coincide.

10. A triangle with two equal angles is an isosceles triangle.

1 1. Two triangles with equal opposite sides of two angles and one angle are the same.

12. The two base angles of an isosceles triangle are equal.

13. The perpendicular lines of the three sides of a triangle intersect at a point, and the distances from that point to the three vertices are equal.

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

15. Within an angle, points with equal distances to both sides of the angle are on the bisector of the angle.

16. The point on the vertical line in the line segment is equal to the distance between the two ends of the line segment.

17. If the sum of squares of two sides of a triangle is equal to the square of the third side, then the triangle is a right triangle.

18. The hypotenuse and the right-angled side correspond to the coincidence of two right-angled triangles.

19. An isosceles triangle with an angle of 60 degrees is an equilateral triangle.

20. In a right triangle, if an acute angle is equal to 30 degrees, then the right side it faces is equal to half of the hypotenuse.

2 1. The square of two right angles of a right triangle is equal to the square of the third side.

22. In a right triangle, the center line of the hypotenuse is equal to half of the hypotenuse.