Letbe the
plane as a subset of
with the Euclidean topology. Let
be the sphere of radius 1 with centre at
Then
is a compactification of
Letbe the line passing through the point
on the sphere
Take any point
in the plane and draw a line through
and
This line will intersect the sphere at a point
We can define a function
from the plane to the sphere in this way.
is one to one and onto
and both
and
are continuous. Hence
is a homeomorphism from the plane to the subset
of
is not compact while
is compact, and the set
is dense in
so that
is a compactification of