http://www.ck12.org Chapter 1. Basics of Geometry
1.9 Linear Pairs
Here you’ll learn what linear pairs are and how they can help you to solve problems.
What if you notice two angles in a picture that make a straight line? What information does this give you about
the angles? After completing this Concept, you’ll be able to apply the properties of linear pairs to help you solve
problems.
Watch This
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Click image to the left for more content.CK-12 Foundation: Chapter1LinearPairsA
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Click image to the left for more content.James Sousa:Linear Pairs
Guidance
Adjacent anglesare two angles that have the same vertex, share a side, and do not overlap. In the picture below,
(^6) PSQand (^6) QSRare adjacent.
Alinear pairis two angles that are adjacent and whose non-common sides form a straight line. If two angles are a
linear pair, then they are supplementary.
(^6) PSQand (^6) QSRare a linear pair.
m^6 PSR= 180 ◦
m^6 PSQ+m^6 QSR=m^6 PSR
m^6 PSQ+m^6 QSR= 180 ◦
Example A
What is the value of each angle?
These two angles are a linear pair, so they are supplementary, or add up to 180◦. Write an equation.