1. Triangles

2. Today’s Objectives
To learn new strategies that will help find the measures of angles in a triangle
To review how to classify triangles

3. Types of Triangles (by sides)
Equilateral
Isosceles
Scalene

4. Equilateral Triangles
Definition:
A triangle with three congruent sides.
Example:

5. Isosceles Triangles Definition: Example:
A triangle with two congruent sides.
Example:

6. Scalene Triangles Definition: Example:
A triangle with no congruent sides.
Example:

7. Types of Triangles (by angle)
Equiangular
Acute
Right
Obtuse

8. Equiangular Triangles
Definition:
A triangle with three congruent angles.
Example:

9. Acute Triangles Definition: Example:
A triangle whose angles are all acute.
Example:

10. Right Triangles
Definition:
A triangle with one right angle.
Example:

11. Obtuse Triangles Definition: Example:
A triangle with one obtuse angle.
Example:

12. Triangle Video
Triangle video!!

13. Triangle Activity Draw and cut out a large triangle.
Number all three angles of the triangle
Tear of the angles
Place the 3 angles adjacent to each other to form one angle
Compare your results with a partner.
Draw conclusions about the sum of the angles of a triangle.

14. The sum of the measures of the angles of a triangle is
Triangle Angle-Sum
The sum of the measures of the angles of a triangle is
always 180.

15. Find the measure of the missing angle
< C = 57°
< a = 87° x
< x = 45° x

16. Practice Find all value for missing angels: <y +70+90=180
<x+40+90=180
<x+130=180
<x=50

17. Practice Find all value for missing angels: <x +83+41=180
<x and <y are vertical angels and therefore, have the same measure

18. Practice Find all value for missing angels: <x + 39 + 65=180
<y + <x = 180
<y +76 = 180
<y = 104
<z + <y + 21 = 180
<z = 180
<z = 180
<z = 55

19. Find the following angle measures.B
<FDC
The following angles are supplementary = 180°
74 + missing angle = 180°
Missing angle = 106 °
<FDC
<D = 180
<D = 180
<D = 17
<ADF
D = 180
164 + D = 180
D = 16
<CDB
The following angles are supplementary = 180°
57 + missing angle = 180°
Missing angle = 123°
<CDB
<D = 180
<D = 180
<D = 12
45°
123° C
57° F
106°
74° A D

20. Homework
Triangles