Find the union of each of the following pairs of sets :
$A = \{ x:x$ is a natural number and $1\, < \,x\, \le \,6\} $
$B = \{ x:x$ is a natural number and $6\, < \,x\, < \,10\} $
$A = \{ x:x$ is a natural number and $1\, < \,x\, \le \,6\} = \{ 2,3,4,5,6\} $
$B = \{ x:x$ is a natural number and $6\, < \,x\, < \,10\} = \{ 7,8,9\} $
$A \cap B=\varnothing$
If $A=\{1,2,3,4\}, B=\{3,4,5,6\}, C=\{5,6,7,8\}$ and $D=\{7,8,9,10\} ;$ find
$A \cup C$
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
If $X=\{a, b, c, d\}$ and $Y=\{f, b, d, g\},$ find
$X \cap Y$
If $A=\{3,6,9,12,15,18,21\}, B=\{4,8,12,16,20\},$ $C=\{2,4,6,8,10,12,14,16\}, D=\{5,10,15,20\} ;$ find
$D-C$
If ${N_a} = \{ an:n \in N\} ,$ then ${N_3} \cap {N_4} = $