for full circle area is π * R² [here R = radius],
for a sector of circle with angle β, area will be = (β/2) * R², β is in radian,
here let β = 22.5° = (π * 22.5/180) = π/8 radian,
now [(π/8)/2] * R² = 9π, [π/16] * R² = 9π
R² = 9 * 16 = 144,
R = √144 = 12 m
