If $A=\{3,5,7,9,11\}, B=\{7,9,11,13\}, C=\{11,13,15\}$ and $D=\{15,17\} ;$ find

$A \cap D$

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

State whether each of the following statement is true or false. Justify you answer.

$\{a, e, i, o, u\}$ and $\{a, b, c, d\}$ are disjoint sets.

Let $A, B$ and $C$ be sets such that $\phi  \ne A \cap B \subseteq C$. Then which of the following statements is not true ?

If $A$ and $B$ are any two sets, then $A \cup (A \cap B) $ is equal to

If $A, B$ and $C$ are non-empty sets, then $(A -B)  \cup (B -A)$ equals