Question

Give one practical use for a hyperbolic trig function

Answer 1

"In real life you use the catenary shape to know how much cable to place between two poles in high power transmission lines. Too much cable and it sags too much making it a hazzard. Too little cable and it breaks due to high tension as it stretches. Quite important to get it right when you have 768kV @ 6000 Amps through the cable."

Check out the discussion at the link posted below:
http://math.stackexchange.com/questions/123/real-world-uses-of-hyperbolic-trigonometric-functions

Answer 2

I was going to say it was to keep engineering students busy on their exams.
But Directrix is much better at this than I.