[tex]\textit{sum of all interior angles in a regular polygon}\\\\ \theta n=180(n-2) ~~ \begin{cases} \theta =\stackrel{degrees}{angle}\\ n=\stackrel{side's}{number}\\[-0.5em] \hrulefill\\ n=13 \end{cases}\implies \theta (13)=180(13-2) \\\\\\ 13\theta =180(11)\implies 13\theta =1980\implies \theta =\cfrac{1980}{13}\implies \theta \approx 152.3^o[/tex]
