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Maths rule
(files.catbox.moe)
Be sure to follow the rule before you head out.
Rule: You must post before you leave.
Did you mean ALL the upside up A?
Nope, it means "for any" as in no matter which one you choose it will be correct.
https://en.m.wikipedia.org/wiki/Universal_quantification
I usually used it as "for all", but its looks like "for any" is used too
I sit corrected. It's used as an arbitrary singular value within the proof, so for any always felt more appropriate.