Thanks! That really helped. Yeah, I've got to learn a lot more Logic.

Thanks a lot.

Thanks for the remark. I don't actually hold that 'if p then necessarily ~p'. raised this problem in my symbolic logic class when my professor stated that the truth of ~p necessarily follows from the falsity of p. And I disagreed and showed him an example(John has stopped taking medicine) where it does not happen.
My doubt is this: Does the falsity of a statement(p) necessarily imply its opposite(~p) is true? (My professor says it does imply.)