quadric

Last updated January 27, 2022

Properties

1. Let $Q$ be a quadric, $Q\subset\mathbb{P}^N$, $p\in Q$ a smooth point, $H\not\ni p$ a hyperplane. Then the projection from $p$ onto $H$ induces an isomorphism $$Q\setminus (Q\cap T_p Q)\cong H\setminus H(H\cap T_p Q).$$