Question

a set is called open set iff its compliment is is a closed set.​

Answer 1

Answer:

First of all we must have an open set, it is a set in which each and every one of its elements are surrounded by elements that also belong to the set or, said in a more intuitive way, that no element of the set also belongs to the border of the set.

In mathematics, in the branch of topology, a closed set is the complement of an open one. An important property of closed sets is that any convergent succession defined in a closed set converges to a value of the set.

Step-by-step explanation: