Program for finding roots and selecting one

[Eugenio]

I am making a program an at some point i need the program to:

1) Find the roots of a cubic polinomi
2) The roots are always going to be 2 complex and 1 real ( cause of the physics behind). And i want the program to select the real one and define it as "Z"
3) Now that Z is define as one number ( the real root out of the three possible) it can continuo with my calculations.

I have the doubt that if I calculate the roots through Cas.function('expresion'), the three routs will come out as a vector, list, matrix or what?