A function is given by a verbal description. Determine whether it is one-to-one. The function f(t) is the height of a football t seconds after kickoff. Yes, it is one-to-one. No, it is not one-to-one. A function is given by a verbal description. Determine whether it is one-to-one. The function f(t) is your height at age t Yes, it is one-to-one. No, it is not one-to-one.