Abstract
In this article, using the local parametric equations of a generic projection π of a smooth projective variety X, at an analytically irreducible singular point y of X′ = π(X), the defining ideals J and J′ of X′ and its singular locus at y are expressed as ideals of maximal and sub-maximal minors of certain Sylvester matrix @. The proof is obtained by a convenient reduction of @ to a “generic pluri-circulant matrix” P and the construction of minimal Gröbner bases for the ideal of t-minors of P and for the ideals J and J′. The depth of local rings of X′ and Sing (X′) at y are also computed in terms of the multiplicity at y.