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JEE Main 2021
Mathematical Reasoning
Mathematical Reasoning
Easy

Question

The Boolean expression ~(p \Rightarrow (~q)) is equivalent to :

Options

Solution

Key Concepts and Formulas

  • Implication: pqpqp \Rightarrow q \equiv \sim p \vee q
  • De Morgan's Laws: (pq)pq\sim (p \vee q) \equiv \sim p \wedge \sim q and (pq)pq\sim (p \wedge q) \equiv \sim p \vee \sim q
  • Double Negation: (p)p\sim(\sim p) \equiv p

Step-by-Step Solution

Step 1: Rewrite the implication using the equivalence pqpqp \Rightarrow q \equiv \sim p \vee q. We are given the expression (p(q))\sim (p \Rightarrow (\sim q)). We want to simplify this. First, we apply the implication equivalence to the expression inside the parentheses: (p(q))(pq)\sim (p \Rightarrow (\sim q)) \equiv \sim (\sim p \vee \sim q) This replaces the implication with an equivalent expression using negation and disjunction.

Step 2: Apply De Morgan's Law. Now we apply De Morgan's Law to the expression inside the outer negation: (pq)\sim (\sim p \vee \sim q). De Morgan's Law states that (pq)pq\sim (p \vee q) \equiv \sim p \wedge \sim q. Thus, we have: (pq)(p)(q)\sim (\sim p \vee \sim q) \equiv \sim (\sim p) \wedge \sim (\sim q) This step transforms the disjunction into a conjunction of negations.

Step 3: Simplify using Double Negation. We apply the double negation rule, (p)p\sim (\sim p) \equiv p, to both terms: (p)(q)pq\sim (\sim p) \wedge \sim (\sim q) \equiv p \wedge q This simplifies the expression to its final form.

Common Mistakes & Tips

  • Remember to apply De Morgan's Laws correctly. It's a common mistake to only negate one of the terms inside the parentheses.
  • Be careful with the order of operations. Negation applies before conjunction and disjunction.
  • When simplifying Boolean expressions, it is often helpful to rewrite implications using the equivalence pqpqp \Rightarrow q \equiv \sim p \vee q.

Summary

We started with the expression (p(q))\sim (p \Rightarrow (\sim q)). By first rewriting the implication using the equivalence pqpqp \Rightarrow q \equiv \sim p \vee q, and then applying De Morgan's Law and the double negation rule, we simplified the expression to pqp \wedge q. This is the final simplified form.

Final Answer

The final answer is \boxed{p \wedge q}, which corresponds to option (A).

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