Matlab is a CAS or Computer Algebra System. It is capable of doing integrals and derivatives. Sums and products. It can graph 2D and 3D functions. It can also do CAD.
I do not cover it here in this thread because I am not a big fan of it. I think that Mathematica and Maple are superior to it for the type of work I do. But with the acquisition of Mupad it will definitely be stronger than before.
Because they graph so well, and can animate objects and do not make arithmetic mistakes they are valuable to provide insight, disprove conjectures, prove assertions by exhausting all the possibilities and checking work for correctness.