Which of the following propositions is tautology?
A.  (p v q)→q 

B.  p v (q→p) 

C.  p v (p→q) 

D.  Both (b) & (c) 

Option: C Explanation : A tautology is a statement that is always true.
Click on Discuss to view users comments. ritu said: (9:06pm on Sunday 20th January 2013)
why c give some explaination
jigyasa gupta said: (9:54am on Thursday 21st March 2013)
evn in option b every condition is a tautology...
sanket said: (9:22pm on Monday 15th April 2013)
why c is ans why not b
badal said: (1:01am on Thursday 25th April 2013)
May i get full explanation about tautology
Nirmal said: (10:14am on Friday 7th June 2013)
Yes why not b?
Srushti said: (8:13am on Friday 12th July 2013)
without writing the truth table how to know whether it is tautology or no?
Nilesh said: (6:03pm on Friday 5th June 2015)
[C] = P (P>q) = p ( ~p q )= p ~p q= ( p ~p ) q= True q= ( True q ) = True
Hina varshney said: (10:37pm on Tuesday 29th August 2017)
Option a is also tautology..

A.  A tautulogy 
B.  A contradiction 
C.  Logically equivalent to p ^ q 
D.  All of above 
Option: C Explanation : Click on Discuss to view users comments. rekha malviya said: (7:55am on Sunday 5th May 2013)
why c..
ajinkya said: (8:03am on Tuesday 2nd July 2013)
B'coz if u solve that eq. geting ans is same as that of p^q
Amarnath said: (2:10am on Thursday 1st August 2013)
 p  q ~p (~pvq)p^(~pvq)p^q 0  0  1  1  0  0  0  1  1  1  0  0  1  0  0  0  0  0  1  1  0  1  1  1 So C is the right answer
Akshita gupta said: (10:31am on Saturday 6th May 2017)
Mah answer Contradiction(B) what is right answer B or C

A.  a v b → b ^ c 
B.  a ^ b → b v c 
C.  a v b → (b → c) 
D.  None of these 
Option: B Explanation : Click on Discuss to view users comments. Srushti said: (8:17am on Friday 12th July 2013)
how its b?

A.  Contradiction 
B.  Valid 
C.  Wellformed formula 
D.  None of these 
Option: D Explanation : Click on Discuss to view users comments. mukesh said: (12:14am on Friday 18th January 2013)
v

A.  P ^ (R v R) 
B.  P ^ (P ^ R) 
C.  R ^ (P v Q) 
D.  Q ^ (P v R) 
Option: D Explanation : Click on Discuss to view users comments. ritu said: (9:54pm on Sunday 20th January 2013)
how plzz explain
rekha malviya said: (8:02am on Sunday 5th May 2013)
how plz explain

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