hi all, i am studying from croom's introduction to topology book. i came across such a question. and i dont have a clue as to how to start . Let X be a metric space with metric d and A a non-empty subset of X. define f:X->IR by : f(x): d(x,A), x E X (x is an element of X) show that f is continuous. also if you can point out a solution book for this book that would be rather nice, considering i am computer scientist studying the topic at home.. thx.