1. Median of a triangle I

2. Median of a triangle II

3. Median of a triangle III

4. Median of a triangle IV

5. Altitude of a triangle I

6. Altitude of a triangle II

7. Altitude of a triangle III

8. Altitude of a triangle IV

9. Exterior angles of a triangle I

10. Exterior angles of a triangle II

11. Exterior angles of a triangle III

12. Apply angle sum property of a triangle I

13. Apply angle sum property of a triangle II

14. Apply angle sum property of a triangle III

15. Apply angle sum property of a triangle IV

16. Special triangles I

17. Special triangles II

18. Special triangles III

19. Special triangles IV

20. Special triangles V

21. Sides of a triangle I

22. Sides of a triangle II

23. Sides of a triangle III