What if you knew that two angles together made a right angle? After completing this Concept, you'll be able to use what you know about complementary angles to solve problems about these angles.
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CK12 Foundation: Chapter1ComplementaryAnglesA
James Sousa: Complementary Angles
Guidance
Two angles are complementary when they add up to
Example A
The two angles below are complementary.
Because the two angles are complementary, they add up to
Example B
The two angles below are complementary. Find the measure of each angle.
Again, the two angles add up to
However, this is not what the question asks for. You need to plug
For
For
Example C
Name one pair of complementary angles in the diagram below.
One example is
Watch this video for help with the Examples above.
CK12 Foundation: Chapter1ComplementaryAnglesB
Vocabulary
Two angles are complementary when they add up to
Guided Practice
Find the measure of an angle that is complementary to

45∘ 
82∘ 
19∘ 
z∘
Answers:
1.
2.
3.
4.
Interactive Practice
Practice
Find the measure of an angle that is complementary to

3∘ 
82∘ 
51∘ 
30∘ 
22∘ 
(x+y)∘ 
x∘
Use the diagram below for exercises 89. Note that
 If
m∠INJ=60∘ , findm∠KNJ .  If
m∠INJ=70∘ , findm∠KNJ .
For 1015, determine if the statement is true or false.
 Complementary angles add up to
180∘ .  Complementary angles are always
45∘ .  Complementary angles are always next to each other.
 Complementary angles add up to
90∘ .  Two angles that make a right angle are complementary.
 The two nonright angles in a right triangle are complementary.