Transcript Perpendicular lines

By Alma Villarreal
Perpendicular
rotate one line 90°
parallel
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Perpendicular Lines in Algebra
If two nonvertical lines are
perpendicular, then their slopes are
negative reciprocals (opposite
reciprocals) of one another, or the
product of their slopes is –1.
Perpendicular Lines in Algebra
Conversely, if the slopes of two lines are
opposite reciprocals of one another, or the
product of their slopes is –1, then the lines
are nonvertical perpendicular lines.
How Perpendicular Lines May Look
Perpendicular lines may also look like this. These
lines are still perpendicular because all the angles
are 90.
Perpendicular Lines
Lines do not have to intersect to be
perpendicular. In the figure below, the two
lines are perpendicular to each other even
though they do not touch.
Perpendicular Lines
You can test if lines are perpendicular by
extending the lines until they cross. If they do
not cross, then they are parallel.
How to Draw Perpendicular Lines
Steps 1 & 2
Step1: Start with a line and point K on that
line.
Step2: Set the compass width to a medium
setting. The actual width does not matter..
Step 3
Step 3: Without changing the compass width,
mark a short arc on the line at each side of the
point K, forming the points P, Q. These two
points are the same distance from K.
Steps 4 & 5
Step4: Mark off an arc on one side of the line.
Step5: With the compass on P, set its width to
any setting beyond K.
Steps 6, 7 & 8
Step6: Without changing the compass width, repeat
from point Q so that the two arcs cross each other,
creating the point R.
Step7: Using the straight edge, draw a line from K to
where the arcs cross.
Step8: Done. The line KR just drawn is
perpendicular to the line PQ at K.