



 
Hi Carlos, Draw a diagram. The two chords in the diagram are of length 6 and 12 units so $DE = 3$ units and $AB = 6$ units. Suppose the radius of the circle is $r$ units and $BC = x$ units then $EC = 2x$ units. Triangles $CAB$ and $CDE$ are right triangles. Pythagoras can help at this point. Penny  


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