[tex]\begin{gathered} \text{The angle of the area is 90\degree, that means that it represents 90/360=1/4 of the circle!} \\ A=\frac{1}{4}A_{circle}_{} \\ \\ A=\frac{1}{4}(\pi r^2) \\ \\ A=\frac{1}{4}\pi(12)^2 \\ \\ A=\frac{1}{4}144\pi \\ \\ A=36\pi \\ \\ \text{ The area is 36}\pi \end{gathered}[/tex]
