a regular polygon has all equal sides.
a PENTA=5, pentagon has 5 sides, so a regular pentagon has 5 equal sides.
[tex] \bf \textit{area of a polygon}\\\\
A=\cfrac{1}{2}ap~~
\begin{cases}
a=apothem\\
p=perimeter\\[-0.5em]
\hrulefill\\
a=K\\
p=\stackrel{3+3+3+3+3}{15}
\end{cases}\implies A=\cfrac{1}{2}K15\implies A=\cfrac{15}{2}K [/tex]
