Video Transcript
If line π΄π΅ is perpendicular
to line πΆπ· and the slope of line π΄π΅ equals two-fifths, find the slope of
line πΆπ·.
Here, we are told that we have
two perpendicular lines π΄π΅ and πΆπ·. Knowing that two lines are
perpendicular means that we know something about the relationship between their
slopes. If we define line π΄π΅ to have
a slope of π sub one and line πΆπ· to have a slope of π sub two, then we know
that π sub two is equal to negative one over π sub one. Given that the slope π sub one
of line π΄π΅ is two-fifths, then π sub two is equal to negative one over
two-fifths. This simplifies to negative
five over two. Because these two lines are
perpendicular, their slopes will be the negative reciprocal of one another. And so the slope of line πΆπ·
is negative five over two.
