Solution (source code)

= Solution

Conjugation differentiates to the <Adjoint representation>
$$
\operatorname{Ad}_gX=\left.\frac d{dt}\right|_{0}g\exp(tX)g^{-1}.
$$
Because conjugations compose, $\operatorname{Ad}_{gh}=\operatorname{Ad}_g\operatorname{Ad}_h$ and $\operatorname{Ad}_e=I$, so this is a group representation.