Help with imaginary number output from CAS - Printable Version +- HP Forums (https://www.hpmuseum.org/forum) +-- Forum: HP Calculators (and very old HP Computers) (/forum-3.html) +--- Forum: HP Prime (/forum-5.html) +--- Thread: Help with imaginary number output from CAS (/thread-1634.html) Help with imaginary number output from CAS - Rich - 06-15-2014 11:35 PM Hi, when "complex" option in the CAS settings is checked, I am getting a "_x" in the output. Is this the correct result and should interpret this as something significant? I think this was seen in an another error earlier but I am unsure if this is what should be expect when having this setting checked. [attachment=834] I have attached a screenshot that has both results, the first with the "complex" checked and the second with it off. Thanks if anyone knows the answer. RE: Help with imaginary number output from CAS - Helge Gabert - 06-16-2014 03:00 AM I have noticed that same "_x" returned with a couple of expressions to be solved as well. While I don't know why it shows up (maybe someone from the HP team knows more), what helped me in those cases was to specify an interval for the solver (e.g., x=-2 .. 2 instead of just x), which returns the solution [-1 1] without any problems (with "complex" checked). [edit: in your case that would be w = -2 . . 2]. RE: Help with imaginary number output from CAS - Nigel (UK) - 06-16-2014 09:31 AM (06-15-2014 11:35 PM)Rich Wrote:  Hi, when "complex" option in the CAS settings is checked, I am getting a "_x" in the output. Is this the correct result and should interpret this as something significant? I think this was seen in an another error earlier but I am unsure if this is what should be expect when having this setting checked. I have attached a screenshot that has both results, the first with the "complex" checked and the second with it off. Thanks if anyone knows the answer. My guess: _x is a free real variable. In other words, for any real value of _x there are two roots for w, given by those two complex expressions. Nigel (UK) RE: Help with imaginary number output from CAS - Rich - 06-17-2014 06:32 AM Thank you, I was able to complete my function with the suggestion of a very wide interval, though I later returned and just made an assumption that w was in the domain of a real integer. For any future reference, this was the command assume(w, DOM_INT).