Whatever the truth value of $$p$$ may be, $$p \vee \left( { \sim p} \right)$$ is always true. Hence, $$p \vee \left( { \sim p} \right)$$ is a tautology.
42.
Which of the following is always true ?
A
$$\left( { \sim p \, \vee \sim q} \right) \equiv \left( {p \wedge q} \right)$$
$$p \Rightarrow \left( { \sim p \vee q} \right)$$ is false means $$p$$ is true and $${ \sim p \vee q}$$ is false.
$$ \Rightarrow p$$ is true and both $$\sim p$$ and $$q$$ are false
$$ \Rightarrow p$$ is true and $$q$$ is false.
47.
The Boolean Expression $$\left( {p \wedge \sim q} \right) \vee q \vee \left( { \sim p \wedge q} \right)$$ is equivalent to:
The inverse of $$p \Rightarrow \, \sim q{\text{ is }} \sim p \Rightarrow q.$$
The contrapositive of $$ \sim p \Rightarrow q{\text{ is }} \sim q \Rightarrow p.$$
[ $$\because $$ contrapositive of $$p \Rightarrow q{\text{ is }} \sim q \Rightarrow \, \sim p$$ ].
49.
Which of the following is true ?
A
$$p \Rightarrow q \equiv \,\, \sim p \Rightarrow \, \sim q$$
B
$$ \sim \left( { p \Rightarrow \, \sim q} \right) \equiv \,\, \sim p \wedge q$$
C
$$ \sim \left( { \sim p \Rightarrow \, \sim q} \right) \equiv \,\, \sim p \wedge q$$
50.
Consider the two statements $$P :$$ He is intelligent and $$Q :$$ He is strong. Then the symbolic form of the statement ‘‘It is not true that he is either intelligent or strong’’ is
Given : $$P :$$ He is intelligent.
$$Q =$$ He is strong.
Symbolic form of
“It is not true that he is either intelligent or strong” is $$ \sim \left( {P \vee Q} \right)$$