I am confused, in some books ,definitions of boundary point and frontier point is same .But some of my friends says both are different . Please explain by examples .
And also closure of a set A is union of A and it's limit points . But is there any counter example which can disprove that closure of A is not union of A and it's boundary point .
At this time according to me "a point p is boundary point of A if every neighbourhood of p contains point of A and complement of A "(may be this definition is wrong )
Best Answer
Your definition of boundary point is correct, and following that definition, the claim
is true and therefore has no counterexample.
As far as the term frontier goes, wikipedia explains
So, there are two different uses of the terms, and you just have to be careful to know which one is used in a given context. And if you are writing, when using the terms, always define them first.