Problem:
A triangle with sides of , and  has both an inscribed and a circumscribed circle. What is the distance between the centers of those circles?
Answer Choices:
A.  
B.  
C.  
D.  
E.  
Solution:
The triangle is a right triangle that can be placed in a coordinate system with vertices at , and . The center of the circumscribed circle is the midpoint of the hypotenuse, which is .

To determine the radius of the inscribed circle notice that the hypotenuse of the triangle is
So the center of the inscribed circle is , and the distance between the two centers is
Answer: .
The problems on this page are the property of the MAA's American Mathematics Competitions