İpucu:
$$B_{d_a}(x,\epsilon)=\left\{\begin{array}{ccc} \{x\} & , & 0<\epsilon \leq 1 \\ \mathbb{R} & , & \epsilon>1 \end{array}\right.$$ ve
$$B_{d_s}(x,\epsilon)=(x-\epsilon,x+\epsilon)$$
ve
$$A^{\circ}=\{x|(\exists \epsilon>0)(B_{d_a}(x,\epsilon)\subseteq A)\}$$
$$\overline{A}=\{x|(\forall\epsilon>0)(B_{d_a}(x,\epsilon)\cap A\neq\emptyset)\}$$
$$A^s=\overline{A}\setminus A^{\circ}$$