W. Kahan
Abstract
The problem concerns four variables a,b,c,d to be interpreted as centre (c,d) and principal semiaxes a,b of an ellipse [EQUATION] We wish to know when E lies inside the unit disk D: x2 + y2 ≤ 1. More precisely, we seek a set of polynomials {Pj(a2, b2, c2, d2,)} for j=1,2,...,n with the property that E≤Dif and only if all Pj(a2, b2, c2, d2,) ≤0. It is known that n> 1, but n should be minimal.
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