Laplace Transform gives "undef" in CAS mode

[frequencydrive]

I am taking a Control Systems class as part of my electrical engineering degree. I have to do some Laplace Transforms regularly so I would like to be able to take the Laplace Transform of a time domain function, but my calculator is really pissing me off.

I am trying to do this in CAS mode (by pusing CAS button). I normally use RPN mode in HOME. But some things seems to be less troublesome if I use CAS mode so that is the mode I am in when trying this stuff. If I type this:

laplace(exp(t)*Sin(t),t,s) the calculator says "undef".

I am not typing in "laplace" I am using the toolbox -> Calculus-> Transform->Laplace. I do not have any user variables defined as 's' or 't'. If I type purge(s,t) the calculator returns ["no such variable s" "no such variable t"].

I have read the manual. On page 370 it shows the following for Laplace Transform:

laplace(exp(x)*sin(x)) gives 1/(x^2-2*x+2)

If I type that the calculator gives me an error stating "undef"

Can someone please help me figure this out? This should be pretty straightforward but it's not going well for me. I am thinking it has something to do with the variables chosen or even capitalization or maybe my CAS settings.

Please help me. I'm dying here.

[parisse]

Check that t,s,x are free variables, purge(t,s,x) if needed. After that laplace(exp(t)*sin(t),t,s) should work.