



 
Grant, Is this the situation you are describing? The chord EA is 20 feet long, D is the midpoint of the chord and the distance from B to D is 7 inches. If this is the correct diagram then the distance from A to D is 240/2 = 120 inches and the distance from D to C is r  7 inches. The triangle ADC is s right triangle so Pythagoras' theorem tell us that
and hence
Expanding gives
Solving for r I get
Let me know if I have misinterpreted your question. Penny  


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences. 