Show that, for all $i \in \llbracket 1 , n \rrbracket$ and all $P \in \mathbb { R } _ { n - 1 } [ X ]$, $$\left\langle L _ { i } , P \right\rangle = P \left( a _ { i } \right).$$
Show that, for all $i \in \llbracket 1 , n \rrbracket$ and all $P \in \mathbb { R } _ { n - 1 } [ X ]$,
$$\left\langle L _ { i } , P \right\rangle = P \left( a _ { i } \right).$$