Definition as velocities of curvesSuppose
is a
manifold (
) and
is a point in
. Pick a chart
where
is an open subset of
containing
. Suppose two curves
and
with
are given such that
and
are both differentiable at
. Then
and
are called equivalent at
if the ordinary derivatives of
and
at
coincide. This defines an equivalence relation on such curves, and the equivalence classes are known as the tangent vectors of
at
. The equivalence class of the curve
is written as
. The tangent space of
at
, denoted by
, is defined as the set of all tangent vectors; it does not depend on the choice of chart
.
To define the vector space operations on
, we use a chart
and define the map
by
. It turns out that this map is bijective and can thus be used to transfer the vector space operations from
over to
, turning the latter into an
-dimensional real vector space. Again, one needs to check that this construction does not depend on the particular chart
chosen, and in fact it does not.
Или любое из двух других определений.