%0 Journal Article %T Expressing the cone radius in the relational calculus with real polynomial constraints %A Floris Geerts %J Computer Science %D 2001 %I arXiv %X We show that there is a query expressible in first-order logic over the reals that returns, on any given semi-algebraic set A, for every point a radius around which A is conical. We obtain this result by combining famous results from calculus and real algebraic geometry, notably Sard's theorem and Thom's first isotopy lemma, with recent algorithmic results by Rannou. %U http://arxiv.org/abs/cs/0106046v1