GEOMETRY LESSON

1. S
3.2: Angles of Triangles

2. What are Interior and Exterior
Angles
S Interior Angles are angles
inside a polygon.
S When the sides of a polygon
are extended, other angles are
formed.
S Exterior Angles are the
angles outside of the
polygon that are adjacent to
the interior angles.

3. Interior Angles Measures of a
Triangle
S The sum of the interior angle
measures of a triangle is 1800
S Algebra
S x+y+z=180

4. Using Interior Angle Measures
Find the value of x.

5. Practice
S 43+x+x-35=180
2x+8=180
2x=172
x=860
S 81+25+x=180
106+x=180
x=740
Find the value of x.

6. Exterior Angle Measures of a
Triangle
S The measure of an exterior
angle of a triangle is equal to
the sum of the measures of the
two nonadjacent interior angles.
S Algebra
S z=x+y

7. Finding Exterior Angle
Measures
Find the measure of the exterior angle.

8. Practice
S 4n-20=n+2n+20
4n-20=3n+20
n-20=20
n=40
Exterior angle= 4(40)-20=160-
0
S y=40+30
y=700
Find the measure of the exterior angle.