circumcircle_hexagon

\documentclass[]{standalone}

\usepackage[]{graphicx}

\usepackage{tikz}
\usepackage{pgfplots}
\pgfplotsset{compat=1.17}
\tikzset{>=latex}
\usetikzlibrary{arrows,arrows.meta}
\usepackage{steinmetz}
\newcommand*{\equal}{=}

\usepackage{tikz-3dplot}
\usetikzlibrary{decorations.markings}

\tikzset{->-/.style={decoration={
  markings,
  mark=at position #1 with {\arrow{>}}},postaction={decorate}}}

\begin{document}
\begin{tikzpicture}[scale=2]
  \draw (0,0) circle [radius=1];
  \draw[thick,-] ({cos(0 r)}, {sin(0 r)}) -- 
  ({cos(1*2*pi/6 r)}, {sin(1*2*pi/6 r)}) --
  ({cos(2*2*pi/6 r)}, {sin(2*2*pi/6 r)}) --
  ({cos(3*2*pi/6 r)}, {sin(3*2*pi/6 r)}) --  
  ({cos(4*2*pi/6 r)}, {sin(4*2*pi/6 r)}) --    
  ({cos(5*2*pi/6 r)}, {sin(5*2*pi/6 r)}) --
  ({cos(6*2*pi/6 r)}, {sin(6*2*pi/6 r)}) circle;
\end{tikzpicture}
\end{document}