Hello,
This was mentioned many times.
You can not do this in SMath (except for some hendheld platforms). Mathcad symbolic engine is MuPad (previously Maple). There has to be someone who is willing to make a "plugin" and to include an additional Symbolic engine into SMath. The "plugin" feature of SMath is ment for extending its abilities by including third part software. Smath might have f.e. Xcas, Maxima or some other free CAS system as a "plugin". Actually, I have no idea if this could be even possible.
Regards,
Radovan
When Sisyphus climbed to the top of a hill, they said: "Wrong boulder!"