My name is Anthony and I take Sequential ][ Math and am taking a practice regents. When doing a logic problem, I encountered the following statements, where I am trying to prove P ( I left out steps unrelated to the question)

Statement	Reason
L	Given
~N --> P	Given
~L v ~N	(acquired from another part of the proof)
~N	?

This is the part I have trouble with. What law is this? I know this is the right answer, but how do you justify it?

I appreciate your help.

Hi Anthony You need to use the definitions of v and of -->. In particular, A --> B is equivalent to ~A v B. Thus statement (3) ~L v ~N is equivalent to L --> ~N, which together with (1) L implies (by modus ponens) (4) ~N. Cheers Chris