Annulus

The area between two concentric circles.

formula

\(A= \pi r_{id}\;^2 - \pi r_{od}\;^2 \)

\(A= \pi \left( r_{id}\;^2 - r_{od}\;^2 \right)\)

Where:

\(A\) = area

\(\pi\) = Pi

\(r_{id}\) = radius (inside diamester)

\(r_{od}\) = radius (outside diameter)