On the figure (
Tangent cone figure 1
)
the
is the closed area bounded by the circle, the
is the origin, the
and
.
On the figure (
Tangent cone figure 2
)
the
is the curved line, the
is the origin, the
and
.
On the figure (
Normal cone figure 1
) the
is the closed area bounded by the curved shape, the
is the origin,
,
and
.
To see that
note that the condition
of the definition (
Normal cone
) requires that
approach
along the boundary of
.
For any other choice of
we have
and
.
Proof
(2).
by definitions and by (1) the
is closed.
