Intersecting the nonvanishing locus with an affine open subset
126094
Hartshorne Algebraic Geometry Exercise II.2.16.
16654
Unions and Intersections of Open Sets are Open
44887
The intersection of two parallel lines
158523
Topology: Proof that a finitely generated cone is closed
43535
show that the interval of the form $[0,a)$ or $(a, 1]$ is open set in metric subspace $[0,1]$ but not open in $\mathbb R^1$
154534
consider the following subsets of complex plane
61816
Cut points and connected space
123304
Locus of the points on complex plane
123656
Covering map between orientable compact connected surfaces without boundary with genus $g$
33734
Every closed subset $E\subseteq \mathbb{R}^n$ is the zero point set of a smooth function
47266
Every affine variety in $\mathbb A^n$ consisting of finitely many points can be written as the zero locus of $n$ polynomials
38581
Construct a Borel set on R such that it intersect every open interval with non-zero non-"full" measure
54690
Proving normality of affine schemes
74796
Extension of intersection of ideals
70048
In which topologies do open sets maintain open under countable or arbitrary intersection?
74330
$\mathbb{R}^n$ not homeomorphic to open subset of $\mathbb{R}^m$
108687
Open subsets in a manifold as submanifold of the same dimension?