[tex]\textit{area of a sector of a circle}\\\\ A=\cfrac{\theta r^2}{2}~~ \begin{cases} r=radius\\ \theta =\stackrel{radias}{angle}\\[-0.5em] \hrulefill\\ r=\frac{8}{3}\\ \theta =\frac{\pi }{2} \end{cases}\implies A=\cfrac{~~ \left( \frac{\pi }{2} \right)\left( \frac{8}{3} \right)^2~~}{2}\implies A=\cfrac{~~ \left( \frac{\pi }{2} \right)\left( \frac{64}{9} \right)~~}{2} \\\\\\ A=\cfrac{~~\frac{32\pi }{9} ~~}{\frac{2}{1}}\implies A=\cfrac{32\pi }{9}\cdot \cfrac{1}{2}\implies A=\cfrac{16\pi }{9}[/tex]
