Description: Anyfinite number of elements in a directed set have a common upper bound. Here is where the nonemptiness constraint in df-drs first comes into play; without it we would need an additional constraint that X not be empty. (Contributed by Stefan O'Rear, 1-Feb-2015)
Ref | Expression | ||
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Hypotheses | drsbn0.b | |
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drsdirfi.l | |
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Assertion | drsdirfi | |