🚀 go-pugleaf

Robert Weinberg (robertw@informix.com) wrote:
: Manhole covers are manufactured in circular shape, rather than oval or square, to  
: satisfy one paramount condition.
: 
: What is the condition, and why does a circular shape satisfy it?
: 
: What other shapes would also satisfy the condition?
: 
Ok, lots of people have already given the correct answer(s) to the first
question, so I won't bother with that.

Somebody mentioned that triangles (with 'circular' edges) are candidates,
too. This is indeed correct.

British 20 & 50p coins are heptagonal - with a constant diameter.

It is therefore tempting to say that any (2n+1) polygon which edges are part
of a circle, with centre being the opposite vertex, will do.

This is, of course, induction of the worst kind. (3 & 7 are true, hence all
odd numbers are true...) Anyone care to prove that these polygons are
suitable as manhole covers?

Radar