- #1
Bashyboy
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Homework Statement
Prove that every segment has a midpoint.
Homework Equations
The Attempt at a Solution
I first began with some arbitrary segment ##AB## in the plane, and then constructed the line ##\overset{\leftrightarrow}{AB} = \ell## from these two points. I then used the theorem which states that, given two points ##A## and ##B## on a line, there exists a point ##C## not on the line such that ##\triangle ACB## is an equilateral triangle. I then was going to use the angle bisector theorem to form a bisector which would intersect the segment ##AB## at a point ##D##. Using the side-side-side criterion of a triangle, I could conclude that ##AD \cong DB##.
However, there are few issues with this. Firstly, how do I know the angle bisector will intersect the segment ##AB##; why is it not possible that the angle bisector ##\overrightarrow{CD}## to curve and loop around in such a way that it never intersects the segment ##AB## nor the line ##\ell##? Secondly, even if it does intersect ##\ell##, how do I know that ##D## is between ##A## and ##B##
For the second issue, I tried a proof by contradiction, but I couldn't identify any contradiction.
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