The region lying between two concentric circles. The area of the annulus formed by two circles of radii 
and 
(with 
)
is
 |
The annulus is implemented in the Wolfram Language as Annulus[
x, y
, 
b,
a
].
In the above figure, the area of the circle whose diameter is tangent to the inner circle and has endpoints at the outer circle is equal to the area of the annulus.
