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 860 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_$_h comment Share Follow See all 10 Comments See all 10 10 Comments reply Arjun commented Sep 22, 2017 reply Follow Share So 2 is not valid? You may also mention any grammatic error in question -- that has more weight in GATE than mathematical logic. 0 votes 0 votes saxena0612 commented Sep 22, 2017 reply Follow Share @ Rajesh R find the meaning of Constructive Dilemma , Destructive Dilemma and Hypothetical Syllogism in Logic chapter in Rosen . you will get it. 1 votes 1 votes Rajesh R commented Sep 22, 2017 reply Follow Share Is there any way to analyse the question from scratch other than byhearting those rules ? @Arjun sir 0 votes 0 votes Arjun commented Sep 22, 2017 reply Follow Share yes, I dont know those rules or never did as our B.Tech. Sir told us to use some stupid text for DS and not Rosen. But I can solve these questions. For "implies", just try to make the RHS false and then try to make LHS true. Then it reduces to an aptitude question. 2 votes 2 votes Rajesh R commented Sep 23, 2017 reply Follow Share Thanks sir, I did the way you mentioned and found out all statements are true. @aish, change your answer if possible. 1 votes 1 votes A_i_$_h commented Sep 23, 2017 reply Follow Share Can someone help out using those rules, how second statement is valid? 0 votes 0 votes Arjun commented Sep 23, 2017 reply Follow Share @Aish For the second, Take p as true -> (going to LHS) which means q is true, ~q is false, ~s is TRUE, r is false. So, whenever p is true, r is false, making RHS true whenever LHS is true. Hence valid. 0 votes 0 votes 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.