1. Triangles A polygon with 3 sides.
Named by the angles or the measure of its sides.

2. Right Triangle Naming by Angles
This Triangle has 1 angle=90°, what is it? T
Right Triangle
90° R S

3. Naming by Angles Acute Triangle
This Triangle has 3 angles that all measure less than 90°, what is it? E
Acute Triangle D F

4. Naming by Angles Obtuse Triangle
This Triangle has 1 angle that measures more than 90°, what is it? Q
Obtuse Triangle P R

5. Naming by Sides Equilateral Triangle
This Triangle has 3 sides of equal length and 3 equal angles that all measure 60°, what is it?
Equilateral Triangle

6. Naming by Sides Isosceles Triangle
This Triangle have at least 2 sides of equal length. (An Equilateral Triangle is a special case of this one.) What is it?
Isosceles Triangle

7. Scalene Triangle Naming by Sides
This Triangle has no sides of equal length and no angles are equal, what is it?
Scalene Triangle

8. The Interior Angles of a add up to equal….
180°

9. Example 1 How many triangles exist with the given angle measures?
10°, 50°, 120°

10. Example 2
How many triangles exist with the given angle measures? 76°, 62°, 25°

11. Example 3 How many triangles exist with the given side lengths?
3 ft, 3 ft, 3 ft

12. 10.4 (7th) Number 2
List the angles of each triangle in order from least to greatest measure.

13. Triangle Inequality Theorem
Any side of a Triangle is always shorter than that the sum of the two other sides.
AB + BC > AC

14. 10.4 (7th) Number 11
Determine whether it is possible to form a triangle using segments with the given measurements. Explain.
10 yd, 5 yd, 21 yd

15. 10.4 (7th) Number 13
Determine whether it is possible to form a triangle using segments with the given measurements. Explain.
112 mm, 300 mm, 190 mm

16. 10.4 (7th) Number 19