P ⊆ coNP

Inclusion · folklore

Statement

P $\subseteq$ coNP — folklore.

Sketch

$\mathbf{P}$ is closed under complement, so for $L\in \mathbf{P}$ the complement $\bar{L}$ lies in $\mathbf{P}\subseteq \mathbf{NP}$ (P ⊆ NP), placing $L$ in $\mathbf{coNP}$.