Use the character map in accessories>>system tools.
Here's my take on infinity:
∞ / x = ∞, where x is any number except ∞
∞ + x = ∞, where x is any number, including ∞
∞ - x = ∞, where x is any number except ∞
∞(x) = ∞, where x is any number except ∞, if it is ∞, then the answer is something called superinfinity. (I guess; I heard it somewhere...)
Sorry for the threadjack...