Quiero trabajar con varias constantes, pero simbolicamente.

There is not much you can do against that error. It stems from Mathacds native numeric engine and does not affect the symbolic part (which is the integrated third party program muPad). You may have noticed, that symbolic operations still work despite the error message.

If you use functions, you may consider defining them in such a way, that those "undefined" variables are used as function arguments. See example below.

You would have better done to attach your worksheet or at least provide a screen shot so we better see, what kind of calculations you are doing and maybe there could be a way to avoid that nasty error message. Just telling us that you try to define function nu(v), etc. is not informative enough.

Here the example, hope it helps:

1) The "intuitive" way, provoking the error message from the numeric processor

2) Using the parameters a and b as function arguments, thus avoiding the error at the cost of more typing work

Regards

Werner

P.S:: If I could use Google translator to find out what your question means, you could have used that translator as well to formulate your question in English, which is the primary language in this forum and you benefit from doing so as you reach a wider audience doing so.

In addition to Werner's reply.

Succes!
Luc