Straightedge and Compass Constructions (2 of 2)

This post contains images based on the straightedge-and-compass constructions discussed in Part 1.

Plotting points

All of the 5743 points that can be drawn using five or fewer lines/circles in a straightedge-and-ruler construction, starting with just the initial points of (0,0) and (1,0).

Peter Kagey (@peterkagey.com) 2025-04-17T23:11:24.354Z

If we don't allow use of the straightedge, we get these 1704 points that can be drawn using five or fewer circles and no lines.There's a theorem called the Mohr–Mascheroni theorem that says that every point that can be determined with a rule and compass can be determined with just the compass!

Peter Kagey (@peterkagey.com) 2025-04-17T23:30:15.092Z
All of the \(5743\) points that can be drawn using five or fewer lines/circles in a straightedge-and-ruler construction, starting with just the initial points of \((0,0)\) and \((1,0)\).
All of the \(1704\) points that can be drawn using five or fewer circles (and no lines) in a straightedge-and-ruler construction, starting with just the initial points of \((0,0)\) and \((1,0)\).

All the circles and lines

Just for fun, here are two other images, the first shows all of the distinct lines and circles you can draw using a ruler-and-compass in at most five steps. The second show all of the distinct circles you can draw within five steps using just a compass.

Here are the 1337 circles and 596 lines that can be drawn using five or fewer lines/circles in a straightedge-and-ruler construction, starting with just the initial points of (0,0) and (1,0).The other image is the 480 circles that can be drawn with a compass alone in under five steps.

Peter Kagey (@peterkagey.com) 2025-04-18T17:52:02.763Z

Comments

2 responses to “Straightedge and Compass Constructions (2 of 2)”

  1. Can you list the best approximations to squaring the circle for each number of steps?

    1. Sure! What do you have in mind exactly? The point that is closest to the circle centered at the origin of radius sqrt(pi)? The line segment containing two points whose distance is approximately pi?

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