Theorem
Let
and
be open balls in a metric space
and let
then a ball open in
exists such that![]()
Proof
Let
and
Suppose
so there exists![]()
Since
there exists an open ball
and since
there exists an open ball![]()

Take
then
and
so![]()
Theorem
Let
and
be open balls in a metric space
and let
then a ball open in
exists such that![]()
Proof
Let
and
Suppose
so there exists![]()
Since
there exists an open ball
and since
there exists an open ball![]()

Take
then
and
so![]()