In: Advanced Math
Let (X,d) be the Cartesian product of the two metric spaces (X1,d1) and (X2,d2).
a) show that a sequence {(xn1,xn2)} in X is Cauchy sequence in X if and only if {xn1} is a Cauchy sequence in X1 and {xn2} is a Cauchy in X2.
b) show that X is complete if and only if both X1 and X2 are complete.