Anyone know of a good unit or introduction online to hyperbolic trig functions which would be good for a pre-calculus level class? Is it worth at least introducing hyperbolic functions to pre-calculus students? I'm ahead of where I'm normally at this time of year in pre-calc, and thought I'd spend a little more time this year on hyperbolic functions, because in calculus, we have about enough time to say, "here are the formulas, here are the derivatives. Pretty similar to the trig derivatives, huh? A sagging telephone line takes the form of a hyperbolic cosine, and they lied to you in algebra when they used the St. Louis Arch as an example of a parabola. It's actually an inverted hyperbolic cosine function."