Paper 4, Section II, G

Analysis II
Part IB, 2010

What does it mean to say that a function ff on an interval in R\mathbf{R} is uniformly continuous? Assuming the Bolzano-Weierstrass theorem, show that any continuous function on a finite closed interval is uniformly continuous.

Suppose that ff is a continuous function on the real line, and that f(x)f(x) tends to finite limits as x±x \rightarrow \pm \infty; show that ff is uniformly continuous.

If ff is a uniformly continuous function on R\mathbf{R}, show that f(x)/xf(x) / x is bounded as x±x \rightarrow \pm \infty. If gg is a continuous function on R\mathbf{R} for which g(x)/x0g(x) / x \rightarrow 0 as x±x \rightarrow \pm \infty, determine whether gg is necessarily uniformly continuous, giving proof or counterexample as appropriate.