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DEFINITION 1 (ALTERNATIVE DEFINITION OF CONTINUITY): We say that f is continuous* at a if lim f(a+ h) = f(a).
Exercise 1: Show that f is continuous at a if and only if f is continuous* at a.
DEFINITION 2 (FIXED POINT, PERIODIC POINT): Let I ⊆ R be an interval, and let f: I → I be a continuous function. We say that a ∈ I is a fixed point of f if f(a) = a. Otherwise, we say that a ∈ I is periodic of period p ∈ N, if p is the smallest positive integer for which we have f(f(...f(a)) = a, p times.