Refer to the figure.
We are looking for the area of the sector of a circle as shown in the figure shaded with green color.
The area of a sector of a circle can be calculated using the formula
![A=(1)/(2)r^2sin\left(\theta \right)](https://img.qammunity.org/2019/formulas/mathematics/high-school/awl8qwiqs351pdgvobm70fzr6uz7kscr0t.png)
where r=radius, and θ=central angle (in radians)
The central angle of the given sector is just one-third of a full circle (2π). That is
![\theta =(2\pi )/(3)](https://img.qammunity.org/2019/formulas/mathematics/high-school/6u52qdt7qspoas562fxd1fn9blsdkh5poo.png)
Now, to solve for the radius of the circle, we can use the formula
![R=(abc)/(4A)](https://img.qammunity.org/2019/formulas/mathematics/high-school/tmps4ukbdfpfhphr7thjt67ki6l9ixw88k.png)
where R is the radius of the circumscribed circle; a,b, and c are the sides of the triangle; and A is the area of the triangle.
The area of the equilateral triangle can be solved using the formula
![A=(√(3))/(4)a^2](https://img.qammunity.org/2019/formulas/mathematics/high-school/1khu6shvshawmvo60u0pq0ikjmcivxm9d3.png)
. That is
![A=(√(3))/(4)a^2=(√(3))/(4)\left(2√(3)\right)^2=3√(3)](https://img.qammunity.org/2019/formulas/mathematics/high-school/p1rxe63yccdl357uc2te8zuju6tckc8fbd.png)
Now, we substitute this area in the formula to solve for the radius of the circle.
![R=(abc)/(4A)=(\left(2√(3)\right)^3)/(4\left(3√(3)\right))=2](https://img.qammunity.org/2019/formulas/mathematics/high-school/dx20j5vatn4yzt8i18lkg4n681l34jm5ni.png)
Finally, we can solve for the area of the sector by substituting the values of the angle θ, and the radius.
![A=(1)/(2)r^2\theta =(1)/(2)\left(2\right)^2\left((2\pi )/(3)\right)=(4\pi )/(3)\:square\:units](https://img.qammunity.org/2019/formulas/mathematics/high-school/w5lhcm8un8grxlle6fuqogmhbvh3uiyw5j.png)