



 
Hi Don, Here is my diagram but I changed the labeling. C is the centre of the circle. Triangles ABC and EDC are both right triangles. Suppose the distance from C to D is $x$ and the radius of the circle is $r.$ You know the lengths of AB, ED and BD. Use Pythagoras' theorem and the triangle EDC to find an expression for $r^2$. Use Pythagoras' theorem and the triangle ABD to find another expression for $r^2$. Set theses expression equal to each other and solve for $x.$ Penny  


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