From the Princeton book for the GRE Subject Test in Maths:
Does 'this topology' in the first blue box refer to the topology in the red box?
In the first blue box, what does it mean for a set to be open in a topology? I mean, should the book have omitted the word 'open' ? The book seemed to have proven that open intervals are members of the topology in the red box.
In the second blue box, what does it mean for a set to be closed in a topology? I'm guessing it means the set's complement is in or is open in the topology (whatever that means) based on the second green box.
I'm not using Princeton as a replacement for textbooks or Schaum's. I'm using Princeton as a guide.
I have done and plan to do more practice exams.
I know topology may be in only at most 2 questions on an exam.