1 votes 1 votes Which among them are valid? How to approach such questions ? Mathematical Logic mathematical-logic discrete-mathematics + – Rajesh R asked Sep 22, 2017 Rajesh R 855 views answer comment Share Follow See all 2 Comments See all 2 2 Comments reply akash.dinkar12 commented Sep 23, 2017 reply Follow Share All 3 are valid... 0 votes 0 votes Tesla_fan commented Aug 5, 2018 reply Follow Share You can apply resolution principle for this kind of questions,you can find it in rosen. Its easy by solving that method instead of remembering a bunch of rules. If you can remember and apply them,its fine .Else read that and try applying. 0 votes 0 votes Please log in or register to add a comment.
0 votes 0 votes To approach these questions , please study rules of inference A_i_$_h answered Sep 22, 2017 • edited Sep 23, 2017 by A_i_$_h A_i_$_h comment Share Follow See all 10 Comments See all 10 10 Comments reply Show 7 previous comments A_i_$_h commented Sep 23, 2017 reply Follow Share Yes :) but i also want to know where i went wrong when i tried with the rules...so want a help with that 0 votes 0 votes Hemant Parihar commented Sep 23, 2017 reply Follow Share 2nd is one of the inference rule known as destructive dilemma. (r --> s) = (~r v s) (~q v ~s) As both s and ~s can't be true simultaneously. This infer that either ~q or ~r is true. Now, (~q v ~r) (p --> q) = (~p v q) As again both q and ~q can't be true simultaneously. Any one of them ~p or ~r has to be true. As from the premises we can reach to the conclusion it is valid. 2 votes 2 votes A_i_$_h commented Sep 23, 2017 reply Follow Share got it :) 1 votes 1 votes Please log in or register to add a comment.