Question

In the space of X=E^1, what is the complement of the following:
(1,2]
[2,+∞)
{1,2,3,4,5}

Answer 1

In the space of $X=E^1$ let us find the complement of the following:

$(1,2],\ [2,+∞),\ \{1,2,3,4,5\}.$

The complement of $(1,2]$ is $(-\infty,1]\cup(2,+\infty).$ The complement of of $[2,+∞)$ is $(-\infty,2).$ And the complement of $\{1,2,3,4,5\}$ is $(-\infty,1)\cup(1,2)\cup(2,3)\cup(3,4)\cup(4,5)\cup(5,+\infty).$