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?
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?