The sum of intern angles of any polygon is represented by the following expression:
[tex]\begin{gathered} (n-2)\cdot180 \\ \text{whre,} \\ n\text{ is the number of vertices} \end{gathered}[/tex]Since a 40-gon, has 40 vertices, the sum of its intern angles would be:
[tex]\begin{gathered} (40-2)\cdot180=6840\text{ degrees} \\ \end{gathered}[/tex]Then, each angle have a measure:
[tex]\frac{6840}{40}=171\text{ degrees}[/tex]