# Truth table combinations giving the same results as independent combination

I am sorry for the title, I have no idea how to call it. Having the truth table for this expression X and (Y or Z), I get 8 rows giving ALL possible combinations between them. When I take the "short-circuiting" (exluding the ones that have no meaning, e.g. TTF as F will never be evaluated because TT is enough) into consideration, only 4 will be left:

TT-
TFT
TFF
F--


When I need a set where each variable gets at least once T or F, it will be exactly the same set. Is it by chance or is it always like that?

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I don't understand the last two sentences. What does "gets at least once" mean? What will be "the same set" as what? And is what "by chance"? – Trevor Wilson Feb 24 at 21:35