What are some alternatives?
When comparing COSMOSWorks and Derive, you can also consider the following products
COMSOL Multiphysics - COMSOL is the developer of COMSOL Multiphysics software, an interactive environment for modeling and simulating scientific and engineering problems.
MATLAB - A high-level language and interactive environment for numerical computation, visualization, and programming
FEATool Multiphysics - FEATool Multiphysics is a fully integrated Finite Element FEM CAE simulation toolbox for Matlab.
GNU Octave - GNU Octave is a programming language for scientific computing.
elmer - Elmer is an open-source software package that solves partial differential equations. Combined with its ability to run various equations in parallel, it is an effective tool for running multiphysical simulations. Read more about elmer.
Xcos - Xcos is a graphical editor to design hybrid dynamical systems models.