4.5. Third Angle Theorem http://www.ck12.org
Guided Practice
Determine the measure of all the angles in the each triangle.
Answers:
1.m^6 A=86,m^6 C=42 and by the Triangle Sum Theoremm^6 B=52.
m^6 Y=42,m^6 X=86 and by the Triangle Sum Theorem,m^6 Z=52.
2.m^6 C=m^6 A=m^6 Y=m^6 Z=35. By the Triangle Sum Theoremm^6 B=m^6 X=110.
- m^6 A=28,m^6 ABE=90 and by the Triangle Sum Theorem,m^6 E=62.m^6 D=m^6 E=62 because they are
alternate interior angles and the lines are parallel.m^6 C=m^6 A=28 because they are alternate interior angles and
the lines are parallel.m^6 DBC=m^6 ABE=90 because they are vertical angles.
Practice
Determine the measures of the unknown angles.