An annulus is a ring-shaped object, the region bounded by two concentric circles. To find its area, we subtract the area of the inner circle from the area of the outer circle:

Area = π(R² - r²)

Where R is the outer radius and r is the inner radius.

• Outer circumference: C₁ = 2πR
• Inner circumference: C₂ = 2πr
• Area: A = π(R² - r²)