On 26/06/2018 10:40, NY wrote:
"Robin" wrote in message
...
On 26/06/2018 09:06, The Natural Philosopher wrote:
On 26/06/18 06:31, Richard wrote:

20P and 50P coins have a constant diameter despite not being circular.

No, they do not.


They do for the normal meaning of "diameter" (which is not confined
circles, spheres or other n-spheres)

I must admit, I would tend to confine the word "diameter" to circular
(or spherical) objects. But let's leave semantics aside.

Fair enough - but the general meaning of "diameter" does apply more
widely. And "diameter" is a lot shorter than eg "the distance between
one edge and the other for a line that goes through the centre"

I had never realised that the flats on a 20p or 50p coin were arranged
so the distance between one edge and the other, for any line that goes
through the centre, was always the same, irrespective of which part of
the flat or point the line happened to go through and even though the
middle of that line may not always coincide with the centre of the coin.

I'm old enough to have "done" the design of the original 50p coin at
school before it was in circulation

Do all polygons with an odd number of sides have the property, or is it
unique to heptagons (7 sides)?

I _think_ it's possible to achieve it with any odd number of corners but
couldn't tell you the parameters that can be fiddled with.



--
Robin
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