Kerodon

$\Newextarrow{\xRightarrow}{5,5}{0x21D2}$ $\newcommand\empty{}$
$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$

Remark 3.2.4.9. Let $f: X \rightarrow Y$ be a morphism of simplicial sets, and let $f': X \rightarrow Y$ be a morphism which is homotopic to $f$. Then $f$ is nullhomotopic if and only if $f'$ is nullhomotopic.