[Geometry] Draw a square

[rabbit]

I meant changing the width of the compass, ie: not closing etc...

Anyway, here is a slightly different answer, animated so you losers can see what's going on.  As said before, the center of each circle is known because of the hole in the paper:



The red lines are a little off because of Photoshop's weird snapping rules, and I didn't feel like screwing with them.  Live with it.

[Sidoh]

How do you find a line perpendicular to the first one you drew?

[rabbit]

By turning the strait edge and erasing when I made a mistake.  You can't see it (since it's Photoshop), but there are a bunch of erased lines.  Also, if you do make a mistake, you won't get a square in the end (the top right corner won't be a....corner), so you know you messed up and can go fix it.  You all seem to have a thing against erasers.  Get over it.

[Sidoh]

I mean in the circle.  When you make a circle, how do you find a diameter perpendicular to the first one you drew?

[iago]

By turning the strait edge and erasing when I made a mistake.  You can't see it (since it's Photoshop), but there are a bunch of erased lines.  Also, if you do make a mistake, you won't get a square in the end (the top right corner won't be a....corner), so you know you messed up and can go fix it.  You all seem to have a thing against erasers.  Get over it.

The problem with that is, you can draw a whole square like that. Draw a straight line, |. Then draw a perpendicular line to it, erasing and fixing it until it's exactly perpendicular. Draw it: |-. Draw a diagonal between the right of the second line and bottom of the first. Draw a perpendicular to that, which forms an "X" between the two lines. Then draw the other two lines as perpendiculars (erasing till they're right) such that they meet at the bottom-right leg of the X. Done, a perfect square with only a ruler.

The idea behind these questions, however, is to find a flawless solution that will guarantee a perfect square with reasonable accuracy, not one that looks to the naked eye like one.

[Camel]

I think a better way of explaining it is to say that the square is anchored to the points. If you were to drag the points around, the square would still be a square.

So, pentagon anyone?