proof hamiltonian circuit is np complete?

For a problem to be classified as in NP-Complete it must be in NP (solvable in non-deterministic polynomial time or verifiable in deterministic polynomial time), and in NP-Hard (at least as difficult as the hardest problems in NP) To prove NP-Hardness, one needs a polynomial time reduction from it to another problem already shown to be in NP Complete. In class we did two such examples: Hamiltonian Circuit as an instance of Travelling Salesman