$$$$
$\begin{array}{l}
{\hspace{0.75em}\cos\left({\frac{{2}\pi}{97}}\right){+}\cos\left({\frac{{70}\pi}{97}}\right){+}\cos\left({\frac{{72}\pi}{97}}\right)}\\
{\scriptsize{=}\frac{1}{32}\left({{-}{1}{+}\sqrt{97}{-}\sqrt{{2}\left({{97}{-}{9}\sqrt{97}}\right)}{+}{2}\sqrt{{97}{-}{5}\sqrt{97}{+}\sqrt{{2}\left({{5141}{-}{517}\sqrt{97}}\right)}}}\\
{\scriptsize\hspace{0.5em}{-}{2}\sqrt{{2}\left({{97}{+}{7}\sqrt{97}{-}\sqrt{{2}\left({{97}{-}{9}\sqrt{97}}\right)}{-}{4}\sqrt{{2}\left({{97}{+}{9}\sqrt{97}}\right)}{-}{2}\sqrt{{97}{-}{5}\sqrt{97}{-}\sqrt{{2}\left({{5141}{-}{517}\sqrt{97}}\right)}}{+}{4}\sqrt{{97}{-}{5}\sqrt{97}{+}\sqrt{{2}\left({{5141}{-}{517}\sqrt{97}}\right)}}{+}{8}\sqrt{{5}\sqrt{97}{-}\sqrt{{2}\left({{517}\sqrt{97}{+}{5141}}\right)}{+}{97}}}\right)}}\right)}
\end{array}$