Question 451913
Find the diameter of the circle for BC = 16 and DC = 28. Round to the nearest tenth.(The diagram is not drawn to scale.) 
http://i54.tinypic.com/32zo07b.jpg
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Draw a line from the point of tangency D to the center of the circle O to make a right triangle with legs of 28 and DO=r=radius, and a hypotenuse of 16+r.
Using pythagorean Theorem:
28^2+r^2=(16+r)^2
28^2+r^2=(16+r)^2
784+r^2=256+32r+r^2
r^2 cancels out
32r=784-256=528
r=528/32=16.5 
Diameter of circle=2r=2*16.5=33.0 (ans)