2. The sum of the angles of a triangle is always 180 degrees.

3. We classify triangles according to the measure of the angles of the triangle.

4. All 3 angles measure less than 90 degrees.

5. One angle measures 90 degrees and the other two angles are acute.

6. One angle that measures more than 90 degrees and the other two are acute.

7. We classify triangles according to the length of the sides of the triangles.

8. The lengths of the sides are not congruent. The lengths are not equal in size.

9. The lengths of two sides are congruent.

10. The lengths of all three sides are equal in size which means they are congruent.

11. Congruent triangles are triangles that are equal in size and shape. They have the same length of the sides and have the same measure of the angles.

12. Side Angle Side

13. Side Side Side

14. Angle Side Angle

15. Polygons A polygon is a many sided closed figure.

16. POLYGONS Triangle-3 sided Quadrilateral-4 sided Pentagon-5 sided Hexagon-6 sided

17. Polygons Heptagon--7sided Octagon--8 sided Nonagon--9 sided Decagon--10 sided

18. Polygons Undecagon--11 sided Dodecagon--12 sided **A regular polygon has equal sides.**

19. All sides are congruent. Opposite sides are parallel. 4 Right Angles.

20. Opposite sides are congruent and parallel. 4 Right Angles.

21. Opposite sides are congruent and parallel.

22. Opposite sides are parallel. All sides are congruent.

23. Has 2 parallel lines.