Let I⊂R be a closed, bounded interval, let B⊂Rn be a closed ball, and let C0(I,B) denote the set of continuous functions from I to B. Define the sup norm
∥f∥∞=t∈Isup∥f(t)∥Rn.
Show that C0(I,B) is a complete metric space with the distance function
d(f,g)=∥f−g∥∞.