Complementary and
Supplementary Angles
Section 2.2
Elena de Soto
Complementary and
Supplementary Angles
Often times we see angles that
measures add up to either a right
angle or a straight angle. These are
Complements and Supplements.
Video on Complementary Angles
http://youtube.com/watch?v=93gal5blsU4
Video on Supplementary Angles
http://youtube.com/watch?v=3gwcv9LSBO8
Complements
• Complementary
angles are two
angles whose sum
is 90° (or a right
angle). Each of the
two angles is called
the complement of
the other.
Practice
• Find the
complement of 58°
Answer=32°
Supplements
• Supplementary
angles are two
angles whose sum
is 180° (or a
straight angle).
Each of the two
angles is called the
supplement of the
other
Practice
• Find the
supplement of 139°
Answer=41°
Sample Proof
Algebraic Problems
An angle and its complement add to a right
angle. An angle and its supplement add to a
straight angle. Since a right angle is 90
degrees and a straight angle is 180
degrees.
The complement of an angle x degrees is (90 - x) degrees.
The supplement of an angle x degrees is (180 - x) degrees.
Algebraic Formula
Find the measure of XVS
Answer=60°
More Practice Problems
For more practice problems, it is
recommended to try book page 70
#12-24
Works Cited
Angles in Geometry. 25 Nov. 2007. Analyze Math. 29 May 2007 <http://www.analyzemath.com/Geometry/angles.html>.
Rhoad, Richard. Geometry for Enjoyment and Challenge. Illinois: McDougal Littell, 1991.
The Math Forum. Drexel. 29 May 2007 <http://mathforum.org/library/drmath/view/53168.html>.