http://www.ck12.org Chapter 3. Parallel and Perpendicular Lines
Example B
Findm^6 2.
Here,m^61 = 66 ◦because they are alternate interior angles.^6 1 and^6 2 are a linear pair, so they are supplementary.
m^61 +m^62 = 180 ◦
66 ◦+m^62 = 180 ◦
m^62 = 114 ◦This example shows why if two parallel lines are cut by a transversal, the same side interior angles are supplementary.
Example C
Find the measure ofx.
The given angles are same side interior angles. The lines are parallel, therefore the angles add up to 180◦. Write an
equation.
( 2 x+ 43 )◦+( 2 x− 3 )◦= 180 ◦
( 4 x+ 40 )◦= 180 ◦
4 x= 140 ◦
x= 35 ◦Watch this video for help with the Examples above.