When factoring polynomials, Xcas won’t introduce complex numbers if they aren’t already being used. For example,
will simply return
but if an expression already involves complex numbers then Xcas will use them;
Xcas also has ways of finding complex roots even when complex numbers are not present; for example, the command cfactor will factor over the complex numbers
If you want Xcas to use complex numbers by default, you can turn on complex mode. In complex mode,
You can turn on complex mode from the CAS configuration screen. This mode is determined by the value of complex_mode; if this is 1 then complex mode is on, if this variable is 0 then complex mode is off. This option will be stored in the configuration file (see subsection 3.5.10), and so can also be set there.