Is this a non empty perfect set with no rational numbers?
12701
Perfect set without rationals
147534
The set of irrational numbers is not a $F_{\sigma}$ set.
74860
Why is the empty set a subset of every set?
129109
Is the set of polynomial with coefficients on $\mathbb{Q}$ enumerable?
4518
How would one go about proving that the rationals are not the countable intersection of open sets?
130297
$A$ be a subset of $[0,1]$ with non-empty interior ; then is it true that $\mathbb Q+A=\mathbb R$?
110677
How is an empty set truly "empty"?
22800
Can $\sqrt{n} + \sqrt{m}$ be rational if neither $n,m$ are perfect squares?
62542
Why is the empty set considered an interval?
125604
Proof that $\mathbb{Z}$ has no zero divisors
34099
Proving that the empty set is unique
51649
prove there is no smallest positive rational number
130418
Is ${\{\emptyset,\{\emptyset\},\{\{\emptyset\}\},\{\{\{\emptyset\}\}\},...\}} $ a set?
86988
Cardinality of the Irrationals
20706
Non-existence of a Surjective Function from a Set to Its Subsets (Cantor's theorem)
67161
No maximum(minimum) of rationals whose square is lesser(greater) than $2$.
24706
Is there a rational number between any two irrationals?