Solution
= Solution
The distinct affine algebraic groups
$$
SL_2(\mathbb C)
\quad\text{and}\quad
PGL_2(\mathbb C)=SL_2(\mathbb C)/\{\pm I\}
$$
both have the <Special linear Lie algebra> $\mathfrak{sl}_2(\mathbb C)$. Quotienting a <Lie group> by a discrete central subgroup does not change its tangent Lie algebra.