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Same. Never seen that symbol in my life. I've seen ¬, ~, !, etc used for not/negation in computer science, math, logic, etc. And some commenters said they used

by qiskit 5y ago

Same. Never seen that symbol in my life. I've seen ¬, ~, !, etc used for not/negation in computer science, math, logic, etc. And some commenters said they used it to mark proof by contradiction, but why is there a need to mark it when you are showing it via proof? A canonical example of proof by contradiction is proving sqrt(2) is not rational. Never have I seen it marked with that symbol. Where would you even mark it? At the beginning with the assumption? Or at the end like QED?

AaronFriel 5y ago
Math degree holder from Iowa, yeah, I've seen and used it many times. The symbol is used when you reach the contradictory statement. Like "1 = 2". "By way of contradiction suppose P, then ..., thus ~P ↯. Therefore ..."
- phogster 5y ago
  To me that reads: I throw your assumption into the GROUND!
- nerdponx 5y ago
  I've actually always wanted a way to mark "the contradiction" once I've obtained it. Thanks!
valtism 5y ago
I was taught it in extracurricular mathematics in Australia. We were taught that it goes at the end of a contradiction proof once the contradiction has been found. We used to write it extra large, like lightning strike. I think of it like a proof mic-drop.