# How can one show that these groups are isomorphic

I am working on this problem saying: $$\text{Inn}(D_8)\cong\text{Inn}(Q_8)$$

I really don't know where can I attack this problem. Thank you

$D_8$ is dihedral group and $Q_8$ is quaternon group, both of order 8.

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The inner automorphisms of any group are simply $G/Z(G)$ since the conjugation map coming from any element in the center is trivial. The centers of $D_8$ and $Q_8$ are both isomorphic to $Z/2$. In the case of $D_8$, the center is generated by the rotation by 180 degrees. In $Q_8$, the center is simply $\{1,-1\}$. It is now not difficult to show that in either case, $Inn(D_8) \cong Z/2 \oplus Z/2 \cong Inn(Q_8)$.