Tautology and Contradiction

IMPORTANT

Tautology and Contradiction: Overview

This topic covers concepts such as Tautology in Mathematical Reasoning, Fallacy/Contradiction in Mathematical Reasoning, Laws of Algebra of Statements, Idempotent Laws of Algebra of Statements, Associative Laws of Algebra of Statements, etc.

Important Questions on Tautology and Contradiction

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Which of the following Boolean expression is a tautology?

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Let p and q be any two propositions.
Statement I: (pq)q~p is a tautology.

Statement II: ~(~pq)(pq)p is a fallacy.

EASY
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The statement [p(pq)]q, is

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The negation of AA~B is

EASY
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For two statements p and q, prove the following relations of logical equivalence.

pqpp~q

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For two statements p and q, prove the following relations of logical equivalence.

pqqpq

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If p and q are two logical statements, then which of the following is not commutative ?

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Let two statements p and q is defined as below

p : 2×4=7,

q : Kota is in London.

Then truth values of these statements: (i)  pq             (ii)  ~pq              (iii)  pqq are

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The statement ~pq~p~q is

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The dual of p~pF is

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The only statement among the following that is a tautology is

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The logical equivalent statement of pq is

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pqpq is equivalent to

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The statement ~pqp is equivalent to

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Let p: Maths is interesting and q: Maths is easy, then p~pq is equivalent to

MEDIUM
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Let p: Maths is interesting and q: Maths is easy, then p~pq is equivalent to

HARD
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Without using truth table, prove that pq~pq is a tautology.

EASY
IMPORTANT

Using the rules of logic, prove the following logical equivalences.

~pqpq~p