PLEASE HELP GEOMETRY!!The area of sector AOB is  20.25 pi ft^2. Find the exact area of the shaded region.

the area of the sector includes the whole sector, namely the triangle and shaded area.

now, if we just get the area of the triangle, and subtract it from the area of the sector, what's leftover is just the area of the "segment", namely the shaded region, check the picture below.

[tex]\bf \stackrel{sector's~area}{20.25\pi }~~~~-~~~~\stackrel{triangle's~area}{\cfrac{1}{2}(9)(9)}[/tex]