notice, a HEXAgon, has HEXA sides, 6 sides
[tex]\bf \textit{area of a regular polygon}\\\\
A=\cfrac{1}{4}ns^2cot\left( \frac{180}{n} \right)\qquad
\begin{cases}
n=\textit{number of sides}\\
s=\textit{length of one side}\\
\frac{180}{n}=\textit{angle in degrees}\\
----------\\
n=6\\
s=8
\end{cases}
\\\\\\
A=\cfrac{1}{4}\cdot 6\cdot 8^2\cdot cot\left( \frac{180}{6}\right)[/tex]
the angle is in degrees, thus, make sure your calculator is in Degree mode, when getting the cotangent