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JEE Main 202117 MarchEvening Shift
Exam
JEE Main
Year
2021
Date
17 March
Shift
Evening Shift
Subject
Mathematics
Chapter
Mathematical Reasoning

JEE Main 2021 · 17 March · Evening Shift · Mathematics · Mathematical Reasoning

If the Boolean expression ( p ∧ q ) ⊛ ( p ⊗ q ) is a tautology,...

If the Boolean expression (p∧q)⊛(p⊗q)( p ∧ q ) ⊛ ( p ⊗ q ) is a tautology, then ⊛⊛ and ⊗⊗ are respectively given by

Options

  1. A→,→\to , \to
  2. B∧,∨∧ , ∨
  3. C∨,→∨ , \to
  4. D∧,→∧ , \to

Correct answer

A. →,→\to , \to

Step-by-step solution

Option (A)\left(A\right)

(p∧q)→(p→q)( p ∧ q ) \to ( p \to q )

We know that a→b= a∨ba \to b = ~ a ∨ b

=(p∧q)⟶( p∨q)= ( p ∧ q ) ⟶ ( ~ p ∨ q )

= (p∧q)∨( p∨q)= ~ ( p ∧ q ) ∨ ( ~ p ∨ q )

Using De Morgan's Law i.e.  (a∧b)= a∨ b,~ \left(a ∧ b\right) = ~ a ∨ ~ b,

=( p∨ q)∨( p∨q)= ( ~ p ∨ ~ q ) ∨ ( ~ p ∨ q )

Using associative law and commutative law i.e. \left(a ∨ b\right) ∨ c = a ∨ \left(b ∨ c\right) \text{ and } a ∨ b = b ∨ a,</p><p></p><p>= ~ p ∨ ( ~ q ∨ q )</p><p></p><p>= ~ p ∨ t</p><p></p><p>= t</p><p>Option</p><p>Option( B )</p><p></p><p>( p ∧ q ) ∧ ( p ∨ q ) = ( p ∧ q )</p><p>Whichisnotatautology.</p><p>Option</p><p>Which is not a tautology.</p><p>Option( C )</p><p></p><p>( p ∧ q ) ∨ ( p \to q )</p><p></p><p>= ( p ∧ q ) ∨ ( ~ p ∨ q )</p><p></p><p>= ~ p ∨ q</p><p>Whichisnotatautology.</p><p>Option</p><p>Which is not a tautology.</p><p>Option( D )</p><p></p><p>( p ∧ q ) ∧ ( p \to q )</p><p></p><p>= ( p ∧ q ) ∧ ( ~ p ∨ q )</p><p></p><p>= p ∧ q</p><p>Whichisnotatautology.</p><p>Hence,thecorrectanswerisoption(A).</p></p><p>Which is not a tautology.</p><p>Hence, the correct answer is option \left(A\right) .</p>

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