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Show that $D_n$ has a normal subgroup isomorphic to $C_n$, with quotient $C_2$

I'm good with the first part but I just don't understand what the last but "with quotient $C_2$" means.

Thanks for any help (sorry for the really simple question)

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up vote 5 down vote accepted

Since $D_n$ has a normal subgroup $H$, with $H\cong C_n$, you are being asked to show that the quotient group $D_n/H$ is isomorphic to the cyclic group of order $2$. This is rather easy to do, since you know exactly what the order of $D_n/H$ is, and how many groups of that order there are.

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Ah thanks I was just confused as to what it was asking but that makes it clear thanks very much – hmmmm Feb 21 '12 at 21:01

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