1. Drill
1) x = 180, solve for x
2) How many degrees do the interior angles of a triangle add up to.
3) What type of triangle has an angle that is 100 degrees and has all three sides of different lengths.

2. 2.1 Triangles

3. Triangle Angle Sum Theorem
The sum of the interior angles of a triangle add up to 180 degrees.

4. Types of Triangles Equilateral: All three sides equal
Isosceles: At least two sides equal
Scalene: No sides are the same
Equiangular: All angles are equal
Acute: All angles are less than 90 degrees
Right: One angles is a right angle (90 degrees)
Obtuse: One angle is greater than 90 degrees

5. Types of Angles Exterior Angles
“w” is the exterior angle because it is adjacent to one of the interior angles.
Remote Interior Angle
“x” and “y” are remote interior angles in reference to “w” because they are the two interior angles not connected to angle “w”.

6. X Y Z W
X + Y 50 60 70
110
110 75 40 65
115
115 30 55 95 85 85 75 45 60
120
120

7. Exterior Angle Theorem
Exterior Angle = Sum of two remote interior Angles

8. 120o yo
50o xo

9. (x+17)° (x+3)° (3x+10)° 45° 57° y° z° 10° 22° a° 40° c° b° a° e° b°
60°
78° c° d°
50°
15° y° z°
60° x°