Solution
= Solution
The <Levi-Civita connection> is a <torsion-free connection>. Its <torsion form> is
$$
T(u,v)=\nabla_uv-\nabla_vu-[u,v].
$$
Since $T=0$,
$$
\nabla_uv-\nabla_vu=[u,v].
$$
In coordinates this is the symmetry $\Gamma^i_{jk}=\Gamma^i_{kj}$ of the <Christoffel symbols>.