I don't see anything related to calculus.

OK, let's try happy guessing based on near to zero information about what you actually see and what you expect.

You might try to type int or diff and see what choices the dynamic assistant can offer.

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I see so much of Maxima here. Is Smath just a sheetlike shell for wxMaxima?

Well, by your non-replies I guess you an answered my question. Not that that's a bad thing, I was just curious.

Wrote

I see so much of Maxima here. Is Smath just a sheetlike shell for wxMaxima?

I do not think we can say that SMath is a shell for wxMAxima. SMath Maxima plugin does not use wxMaxima but uses Maxima. The Maxima plugin (as well as Maple plugin) appeared and were made by the good willing people because SMath has rather problematic symbolic engine in its core. Moreover, As SMath is similar to Mathcad in its graphical interface, I think we can not say that Mathcad is a shell for Maple or MuPAD symbolic engines. However, I do not think you can use Mathcad separately from these engines, but you can use Smath without Maxima or Maple plugins.

Regards,
Radovan