Co(A) ={f belongs to C(A);f(x)=0 for all x belongs A\K where K C A is a compact set}is the set of continuous functions with compact support.

L1(A):= is the set of integrable functions such that (Integral)(f) <oo

A:=is open and limited

Co(A)is dense in L1(A)

how can i proof these?

Thank's