Proving that $R_2$ with the standard topology is normal?
124179
Proof that every metric space is normal
143831
Showing $\mathbb{Q}$ is homeomorphic to $\mathbb{Q}^2$
102485
Showing that a topological space is ${\rm T}_1$
127491
Isometric isomorphism between $R^2$ and $R$
44934
Show that every normal subgroup can be written as an intersection of $\ker \chi$'s for $\chi \in \operatorname{Irr}(G).$
157488
Proving that $k[x,y,z]/(xz - (y^2 + 1))$ is a normal ring.
138825
The strong topology on $U(\mathcal H)$ is metrisable
93596
If $H\leq G$ and $[G:H]=2$, then $H$ is normal in $G$.
61962
Show $R$ is right-Artinian but not left-Artinian
125761
Is this proof for Theorem 16.4 Munkres Topology correct?
89190
Why is it true that $|AB:A|=|B:A\cap B|$ even if $A$ is not normal in $AB$? (Second Isomorphism Theorem)
90449
Showing that a Sylow subgroup of a group of order $p^{2}q$ is normal.
59424
Showing that $B=\{(x,y) \in \Bbb{R^2} \mid \ xy>0 \}$ is an open set
48607
If $A$ is normal and $A$ and $B$ commute, then $A^*$ and $B$ commute
44453
Prove that the normalisation of $A=k[X,Y]/(Y^2-X^2-X^3)$ is $k[t]$ where $t=Y/X$ (Reid, Exercise 4.5)
12104
How to prove this result involving the quotient maps and connectedness?
64920
Boundary Question in $\mathbb{R}^{2}$ (Manifolds)