Math CentralQuandaries & Queries


Question from Arman:

Two concentric circles have their centre's at point C. The radius of the smaller circle is 8 cm. The length of chord AB is 26 cm and is tangent to the smaller circle. What is the circumference of the larger circle?

Hi Arman,

I drew a diagram of what you described and added a point $D$ where the chord is tangent to the smaller circle.


It looks like $D$ is the midpoint of $AB.$ Can you prove that it is? What is the length of $AC?$


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