What if you were given two supplementary angles? How would you determine their angle measures? After completing this Concept, you'll be able to use the definition of supplementary angles to solve problems like this one.
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CK12 Foundation: Chapter1SupplementaryAnglesA
James Sousa: Supplementary Angles
Guidance
Two angles are supplementary when they add up to
Example A
The two angles below are supplementary. If
Set up an equation.
Example B
What are the measures of two congruent, supplementary angles?
Supplementary angles add up to
So, two congruent, supplementary angles are right angles, or
Example C
Name one pair of supplementary angles in the diagram below.
One example is
Watch this video for help with the Examples above.
CK12 Foundation: Chapter1SupplementaryAnglesB
Vocabulary
Two angles are supplementary when they add up to
Guided Practice
Find the measure of an angle that is supplementary to
1.
2.
3.
4.
Answers:
1.
2.
3.
4.
Interactive Practice
Practice
Find the measure of an angle that is supplementary to

112∘ 
15∘ 
97∘ 
81∘ 
57∘ 
(x−y)∘ 
(x+y)∘
Use the diagram below for exercises 89. Note that
 Name another pair of supplementary angles.
 If
m∠INJ=63∘ , findm∠JNL .
For exercises 1013, determine if the statement is true or false.
 Supplementary angles add up to
180∘ .  Two angles on a straight line are supplementary angles.
 To be supplementary, two angles must be touching.
 It's possible for two angles in a triangle to be supplementary.
For 1415, find the value of