\(\Int(A)=(1,2)\text{,}\) \(\overline A=\{0\}\cup[1,2]\text{,}\) \(\Bdry(A)=\{0,1,2\}\text{,}\) \(A'=[1,2]\text{,}\) dan \(A^i=\{0\}\text{.}\) Himpunan \(A\) tidak terbuka dan tidak tertutup.