Math CentralQuandaries & Queries


Question from maribie, a student:

two circles are concentric. the tangent to the inner circle forms a chord of 12cm in the larger circle. find the area of the "ring" between the two circles?

Hi Maribile,

Suppose that the radius larger circle is $R$ and the radius of the smaller circle is $r.$ Write an expression for the area of the ring between the two circles.

Next look at a diagram of the two circles.


$AB$ is perpindcular to $CA$, do you see why?

What does Pythagoras say about the triangle $ABC?$



About Math Central


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.
Quandaries & Queries page Home page University of Regina PIMS