http://www.ck12.org Chapter 3. Parallel and Perpendicular Lines
First, these two angles form a linear pair. Second, from the marking, we know that^6 ST Cis a right angle. Therefore,
m^6 ST C= 90 ◦. So,m^6 CT Ais also 90◦.
Example B
Determine the measure of^6 1.
From Theorem #1, we know that the lower parallel line is also perpendicular to the transversal. Therefore,m^61 =
90 ◦.
Example C
Findm^6 1.
The two adjacent angles add up to 90◦, sol⊥m. Therefore,m^61 = 90 ◦.
Watch this video for help with the Examples above.