2011-04-09, 01:02 PM
Just to add-on, if you are talking about the double arrow in mathematics
<==>
Like someone said, it means "if and only if"
In order to prove it, you have to prove it in one direction, and then prove it in the other
i.e. Prove that p --> q, and q --> p
If you want to deny it, you only have to disprove one of them i.e. Make a contradiction happen in either direction
<==>
Like someone said, it means "if and only if"
In order to prove it, you have to prove it in one direction, and then prove it in the other
i.e. Prove that p --> q, and q --> p
If you want to deny it, you only have to disprove one of them i.e. Make a contradiction happen in either direction