Polynomial integration on regions defined by a triangle and a conic

Abstract

We present an efficient solution to the following problem, of relevance in a numerical optimization scheme: calculation of integrals of the type \[\iint_{T \cap \{f\ge0\}} ϕ_1ϕ_2 \, dx\,dy\] for quadratic polynomials $f,{\varphi }_1,{\varphi }_2$ on a plane triangle $T$. The naive approach would involve consideration of the many possible shapes of $T\cap \{f\ge 0\}$ (possibly after a convenient transformation) and parameterizing its border, in order to integrate the variables separately. Our solution involves partitioning the triangle into smaller triangles on which integration is much simpler.

8 pages, accepted by ISSAC 2010