http://www.ck12.org Chapter 3. Parallel and Perpendicular Lines
Example 4:Isl⊥m? Explain why or why not.
Solution:If the two adjacent angles add up to 90◦, thenlandmare perpendicular.
23 ◦+ 67 ◦= 90 ◦. Therefore,l⊥m.
Know What? Revisited
Half Dome is vertical and the slope of any vertical line is undefined. Thousands of people flock to Half Dome to
attempt to scale the rock. This front side is very difficult to climb because it is vertical. The only way to scale the
front side is to use the provided cables at the base of the rock. http://www.nps.gov/yose/index.htm