1. Triangles

2. Triangles
Three sides
Three angles
Measures a total of 180°

3. Triangles
Equilateral
Isosceles
Scalene

4. Triangles
Equilateral
Three equal sides
Three equal angles, always 60°

5. Triangles
Isosceles
Two equal sides
Two equal angles

6. Triangles
Scalene
No equal sides
No equal angles

7. Which is which?

8. Practice
Work on the following handout

9. Triangles
Right
Obtuse
Acute

10. Triangles
Right Triangle
A triangle with a right angle

11. Triangles Right Triangle Isosceles Right One right angle
Two other equal angles always of 45°
Two equal sides
Scalene Right
Two other unequal angles
No equal sides
60°
30°

12. Triangles
Acute Triangle
A triangle with all angles less than 90°

13. Triangles
Obtuse Triangle
A triangle with one obtuse angle

14. Which is which?

15. Triangle Properties
The sum of the interior angles is always 180 degrees

16. Triangle Properties
If you need to find the missing angle inside a triangle:
Find the sum of the known angles
Subtract this sum from 180
70° + 50°
120°
180°-120°
60°
a=60°

17. Triangle Properties

18. Practice
Work on the following handout

19. Triangle Properties
Interior and Exterior Angles are supplementary

20. Triangle Properties Interior and Exterior Angles are supplementary

21. Triangle Properties
Interior and Exterior Angles are supplementary

22. Practice
Work on the following handout

23. Triangle Properties
The longest side of a triangle is opposite the largest angle
30°
100°
50°

24. Which is the longest?

25. Practice
Work on the following handout