I started the ruler and compass series a while ago and am just now getting back to it. Here is my construction of a perpendicular bisector of a given line segment.
First, I drew a line segment:
Using my compass (which quickly gave out on me), I made two big fat arcs. They have the same radius — this is important.
Where those two cross, I drew a line. That line is the perpendicular bisector of the original segment (which means it makes a 90° angle and splits it into two equal parts):
Why does it work?
Well, that’s a great question. I’m sure there’s some proof of why this actually results in splitting the original line segment in half with a perpendicular line. I’ll have to think on it more.
But intuitively it totally feels right.
Now that’s a bad way to proceed with math, but it’s a great first start!
How about you?
Do you like to play with ruler and compass constructions? Do you know why this works?
Oh — and if you don’t have one, buy a compass here (that’s the one I just bought to replace my junky one).
And I also ordered this cool book about Compass Drawings — I’m so excited!
Share your thoughts in the comments or on twitter/x.
