  The Isabelle/HOL proof assistant has a powerful library for continuous
analysis, which provides the foundation for verification of hybrid systems.
However, Isabelle lacks automated proof support for continuous artifacts, which
means that verification is often manual. In contrast, Computer Algebra Systems
(CAS), such as Mathematica and SageMath, contain a wealth of efficient
algorithms for matrices, differential equations, and other related artifacts.
Nevertheless, these algorithms are not verified, and thus their outputs cannot,
of themselves, be trusted for use in a safety critical system. In this paper we
integrate two CAS systems into Isabelle, with the aim of certifying symbolic
solutions to ordinary differential equations. This supports a verification
technique that is both automated and trustworthy.
