Circles

Circles, the only closed shape with no edges or bends (except for an oval - the overweight circle). In the book Flatland, by Edwin A. Abbot, (see: http://www.geom.uiuc.edu/~banchoff/Flatland/), a story about a life in two dimensions, circles are the highest class or the priestly order, hence they are the perfect shapes.

The equation of a circle is the following:

Circles may appear in many areas of mathematics, but what about the world we live in? Just think of all the objects that are in the shape of a circle.

We wouldn't have the transportation systems that we have if it wasn't for circles (i.e. wheels). At the carnival most of the rides wouldn't exist. Would we have square plates and cups? Would we invent screws that fit into triangular holes? What would the people who sees UFO's tell us they look like?

So many things just wouldn't make sense without the circle shape. I agree with Edwin Abbot, that circles are definitely the highest class of two dimensional shapes. Lets take a moment to appreciate the circle.

All that aside, here follows a few useful formulas when performing calculations with circles.

Circumference: 2пr

Area: пr²

Diameter: 2r

Arc length:  rθ

r: radius

θ: angle between two lines both from the center of the circle to somewhere on the edge.

Happy circling!

(Flatland also available at Amazon (the book) or eBay (the CD).)