It is NOT a 'countable set'. It is an infinite set. 1, 3, 5, 7, 9, 11, ... you can count to infinity and keep going.
By definition, it is the set of all real numbers!
Are disjoint and complementary subsets of the set of real numbers.
all finite set is countable.but,countable can be finite or infinite
The set of Natural Numbers is the set of 'counting numbers' {1,2,3,4,....}. All of them are also real numbers.
No, it is uncountable. The set of real numbers is uncountable and the set of rational numbers is countable, since the set of real numbers is simply the union of both, it follows that the set of irrational numbers must also be uncountable. (The union of two countable sets is countable.)
It is uncountable, because it contains infinite amount of numbers
Yes. the set of rational numbers is a countable set which can be generated from repeatedly taking countable union, countable intersection and countable complement, etc. Therefore, it is a Borel Set.
Yes, since the set of real numbers can be expressed as a countable union of closed sets.In fact if we're talking about subsets of the real numbers (R), then by definition R is in all sigma-algebras of R including the Borel sigma-algebra, and so is a Borel set.
Countably infinite means you can set up a one-to-one correspondence between the set in question and the set of natural numbers. It can be shown that no such relationship can be established between the set of real numbers and the natural numbers, thus the set of real numbers is not "countable", but it is infinite.
the set of real numbers
It is NOT a 'countable set'. It is an infinite set. 1, 3, 5, 7, 9, 11, ... you can count to infinity and keep going.
real numbers
By definition, it is the set of all real numbers!
The derived set of a set of rational numbers is the set of all limit points of the original set. In other words, it includes all real numbers that can be approached arbitrarily closely by elements of the set. Since the rational numbers are dense in the real numbers, the derived set of a set of rational numbers is the set of all real numbers.
The set of all real numbers (R) is the set of all rational and irrational numbers. The set R has no restrictions in its domain and so includes (-∞, ∞).
The question is a bit vague. The set of all natural numbers N (0,1,2,...) has no 'end', there is no 'largest number', in other words: it has an infinite amount of elements. The set of all real numbers R (which includes -2,sqrt(3), pi, e, 56/8, etc.) als has infinitely many elements, but there is a difference between the two: N is a countable set (you can 'count' all the elements), but R is not. If you want to know more about this, you should search after terms like cardinality, countable set, aleph, ...