Paper 3, Section I, 3G

Metric and Topological Spaces
Part IB, 2011

Let X,YX, Y be topological spaces, and suppose YY is Hausdorff.

(i) Let f,g:XYf, g: X \rightarrow Y be two continuous maps. Show that the set

E(f,g):={xXf(x)=g(x)}XE(f, g):=\{x \in X \mid f(x)=g(x)\} \subset X

is a closed subset of XX.

(ii) Let WW be a dense subset of XX. Show that a continuous map f:XYf: X \rightarrow Y is determined by its restriction fW\left.f\right|_{W} to WW.