Exercise 5.3.5.4. Give a direct proof of Corollary 5.3.5.3 (which does not use the characterization of Proposition 5.3.5.2).
$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
Exercise 5.3.5.4. Give a direct proof of Corollary 5.3.5.3 (which does not use the characterization of Proposition 5.3.5.2).