Cycle Graph is Hamiltonian

Theorem
Let $n \in \Z$ be an integer such that $n \ge 3$.

Let $C_n$ denote the cycle graph of order $n$.

Then $C_n$ is Hamiltonian.

Proof
A undirected graph that contains a cycle that contains every vertex of the graph (but not necessarily every edge).

A cycle graph is a graph which consists of a single cycle.

So all the vertices of $C_n$ are on the same cycle.

The result follows.