Solution
= Solution
Directly commuting the vector fields gives
$$
[T_a,T_b]
=(\mu_a{}^s\partial_s\mu_b{}^r
-\mu_b{}^s\partial_s\mu_a{}^r)\partial_r.
$$
Using the definition in part x and $\lambda\mu=I$ yields
$$
\boxed{[T_a,T_b]=f^c{}_{ab}T_c}.
$$