The Locus of the point at which two given Circles possess the same Power is a straight line Perpendicular to the line joining the Midpoints of the Circle and is known as the chordal (or Radical Axis) of the two Circles.

**References**

Dörrie, H. *100 Great Problems of Elementary Mathematics: Their History and Solutions.* New York: Dover, p. 153, 1965.

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1999-05-26