In: Advanced Math
Euclidean metric) The metric
d
((
x
1
,x
2
)
,
(
y
1
,y
2
)) =
√
(
x
1
−
x
2
)
2
+ (
y
1
−
y
2
)
2
on
R
2
generates the standard (product) topology on
R
2
.
The given metric is
First we prove that the metric topology is contained in the
product topology on
.
Let
be a point in
and
be an open set of metric topology such that
. Since
is
open, there exists an open ball
centred at
and
.
Now for small ,
is an open set in product topology which contains
and is contained in
.
Thus the Euclidean metric topology on
is contained in the product topology on
.
For the converse, let be a point in
and
be an open set of product topology such that
. Since
is
open ,there is an open set
which is contained in
for small enough
.
Now observe that the ball centred at with radius
is contained in
and this ball is an
open set in the metric topology and further
and so the converse is also proved.
And therefore, the metric topology on
is same as the product topology on
.