Even Wikipedia shows that you are wrong. Here is again an example of tautology:The expression "r=0 ≠ r>0" is always resulted by T as its truth value, or in other words, it is a tautology (In logic, a tautology (from the Greek word ταυτολογία) is a formula which is true in every possible interpretation (http://en.wikipedia.org/wiki/Tautology_(logic))).
If one does not agree about it, he has to provide a False result to "r=0 ≠ r>0" expression.
Let @ be some logical connective. Then
(a<b @ c<d) is True
(a<b @ c>d) is True
(a>b @ c<d) is True
(a>b @ c>d) is True
is tautology.
Your expression "r=0 ≠ r>0" lacks the necessary premise options for tautology to exist, but the main problem is that ≠ is not a logical connective. The inequality r>0 is just the only true (metrics) alternative to r≠0 and vice versa when r is a radius of a circle - the expression is not tautology, as opposed to "belongs AND doesn't belong". Remember?
What is "an obvious center?"Also Circumradius (does not related to an obvious center) ≠ Radius (does related to an obvious center), and also this case is a tautology.
Look again at the definition of radius applied to regular polygon,
http://www.mathopenref.com/polygonradius.html
and then reconsider your inequality Radius≠Circumradius by looking at this:
http://etc.usf.edu/clipart/43400/43444/5c_43444_lg.gif
Then digest the fact that "circumradius" derives from the word "circumscribe." In both cases the magnitude of r is the same for the regular polygon and the circumscribed circle. Polygons aside, still, your initial reference to the radius was a case of insufficient definition, coz radius can apply to sphere as well as circle.
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