Proving that subgroup of Rotations in $D_{2n}$ is a normal subgroup
6134
Some Subgroup of Dihedral Group is Normal
125244
Equivalent definitions of normal subgroups
113357
Groups of order $pqr$ and their normal subgroups
102622
K is a subgroup of G. Show that K is not a normal subgroup
12667
How many subgroups of order $n$ does $D_n$ have?
113013
Let $M$ and $N$ be two normal subgroups of $G$. Show that $M \cap N$ is also normal in $G$. Then show that $G/(M \cap N) \cong (G/M) \times (G/N)$
43651
Normal subgroups and factor groups
55493
Showing that the path-connected component of the identity matrix in a subgroup of $GL_n(\Bbb R)$ is a normal subgroup
45580
Intersection of conjugate subgroups is normal
118894
Cyclic subgroup of dihedral group
37928
Isomorphism between $D_{2n}/Z(D_{2n})$ and $D_n$
137691
What are the self-normalizing subgroups of $S_n$?
154398
Show that H is a subgroup of G
98352
If $k|n$, then $D_{2n}/\langle{r^k}\rangle\cong D_{2k}$
85508
Prove that $G$ is an abelian group if $\{(g, g):g\in G\}$ is a normal subgroup.
148285
Generator of group $D_n$
57227
Maximal normal $\pi$-subgroups and torsion subgroups