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Complex Descartes circle theorem. (English)
Am. Math. Mon. 121, No. 10, 927-931 (2014).
Summary: We present a short proof of the Descartes circle theorem on the “curvature-centers” of four mutually tangent circles. Key to the proof is associating an octahedral configuration of spheres to four mutually tangent circles. We also prove an analog for spheres.
Classification: G75
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