Ex 1. (a) Show that the intersection of two domains D and E in C is also a domain. Is the union DUE also a domain? Give reasons. Reference: Definition 1.5: By a domain D in C is meant an open, connected subset of C. Some texts may call such Da region in C. Some texts may also refer to D as a region, if it is a domain containing some of its boundary points. We shall denote a region in C by G of R.