MathDB
Putnam 1996 A2

Source:

June 4, 2014
Putnamcollege contests

Problem Statement

Let C1\mathcal{C}_1 and C2\mathcal{C}_2 be circles whose centers are 1010 units apart, and whose radii are 11 and 33. Find, with proof, the locus of all points MM for which there exists points XC1,YC2X\in \mathcal{C}_1,Y\in \mathcal{C}_2 such that MM is the midpoint of XYXY.