Let $P=\{\theta: \sin \theta-\cos \theta=\sqrt{2} \cos \theta\}$ and $Q=\{\theta: \sin \theta+\cos \theta=\sqrt{2} \sin \theta\}$ be two sets. Then
$P \subset Q$ and $Q-P \neq \varnothing$
$Q \not \subset P$
$P \not \subset Q$
$P=Q$
If $A$ and $B$ are two sets, then $A \cup B = A \cap B$ iff
If $X$ and $Y$ are two sets such that $n( X )=17, n( Y )=23$ and $n( X \cup Y )=38$
find $n( X \cap Y )$
If ${N_a} = [an:n \in N\} ,$ then ${N_5} \cap {N_7} = $
If $A=\{3,5,7,9,11\}, B=\{7,9,11,13\}, C=\{11,13,15\}$ and $D=\{15,17\} ;$ find
$A \cap C$
State whether each of the following statement is true or false. Justify you answer.
$\{2,3,4,5\}$ and $\{3,6\}$ are disjoint sets.