Suppose T \in \mathcal{L}(V), and U \subset V, an invariant subspace under T. Then:
\begin{equation} T|_{U}(u) = Tu,\ \forall u \in U \end{equation}
where T|_{U} \in \mathcal{L}(U)
Suppose T \in \mathcal{L}(V), and U \subset V, an invariant subspace under T. Then:
where T|_{U} \in \mathcal{L}(U)