1. False.
Consider the group "D_4 =<r,s \\mid r^4=s^2=1,rs=sr^{-1} >".
and "\\Z_4=\\{0,1,2,3,4,5,6,7 \\}"
Where "D_4" is dihedral group of order 8 and "\\Z_8" is a additive group of integer modulo 8.
Both "D_4 \\ and \\ \\Z_8" have order 8 but "D_4" is not isomorphic to "\\Z_8"
because "D_4" is non abelian and "\\Z_8" is abelian.
2.True.
Since "A \\cup B=\\{ x:x\\in A \\ or \\ x\\in B \\}=\\phi"
Therefore,"A=B=\\phi" .
Hence,"A\\cap B=\\phi" .
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