[Coda]

If you stop, and you let it keep swinging on its own, then in an ideal system it would just keep moving forever like a planet in orbit. In reality, there's friction that will bleed off that momentum in the form of heat, and it'll spiral towards the center.

A polynomial is just ax^m + bxⁿ + ... + k. Nothing fancier about it than that. The degree of the polynomial is the highest exponent that appears in it. Cosine and sine aren't polynomials because they're not sums of multiples of powers of a single variable. (That said, there are polynomial approximations of those functions, such as Taylor series.) I'm not sure what the "type" of a polynomial is because that's a rather vague term and it could mean several things.