MikeMHz

Hey, so I think I know how to do disjunction elimiation... Where I am given A∨B I can assume A => C and B => C, so the result is C after disjunction elimination. Is this always the correct method? For example if I am given: A∨B --- ∨E A How can I prove that this is not sound? Simply by doing what I did above?

I have been asked to translate into English a number of statements written in set notation based on this introduction. Can somebody talk me through exactly what is being said here? Also, two of the questions use "." to separate terms. I know "Ǝ" means "there exists" and "∀" means "for all"... but what about "."?