Geometry
The formula for the area of a sector is
[tex]k = \frac{m}{360} \times a[/tex]
Input the things which you already know. (m)
[tex]k = \frac{45}{360} \times a[/tex]
a=πr^2
a=36π
Input this into the equation.
[tex]k = \frac{45}{360} \times 36 \times 3.14[/tex]
[tex]k = \frac{45}{360} \times 113.04[/tex]
[tex]k = 14.13[/tex]