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Annulus
Washer

The region between two concentric circles which have different radii.

 

Area of annulus \( = \pi \left( {{R^2} - {r^2}} \right)\)

This is an annulus. It is the region between two concentric circles. The larger circle has radius uppercase R and the smaller has radius lowercase r. 

 


  this page updated 19-jul-17
Mathwords: Terms and Formulas from Algebra I to Calculus
written, illustrated, and webmastered by Bruce Simmons
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