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Line Bisector
From Latin: bi - "two" , secare "to cut,"
Definition: A line which cuts a line segment into two equal parts.
Try this Drag one of the orange dots at A or B and note the the line AB always
divides the line PQ into two equal parts.
(If there is no image below, see support page.)
In general 'to bisect' something means to cut it into two equal parts. The 'bisector' is the thing doing the cutting.
With a line bisector, we are cutting a line segment into two equal lengths with another line - the bisector.
In the figure above, the line
PQ
is being cut into two equal lengths (
 PF and
FQ
) by the bisector line
AB .
If
AB
crosses at a right angle, it is called the "perpendicular bisector" of
PQ
. If it crosses at any other angle it is simply called a bisector.
Drag the points A or B and see both types.
For obvious reasons, the point F is called the midpoint of the line
PQ .
See also angle bisector. How to bisect a line
Obviously, one way to bisect a line segment is to measure its length, divide that by two and mark the midpoint.
But you can do it without any measurement at all using just a compass and straightedge using techniques developed thousands of years ago by the Greeks. For an animated demonstration of how to do this see Perpendicular bisector of a line segment Other line topics
(C) 2007 Copyright John Page
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