Haruki's Theorem

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Short description: Geometry Theorem
Illustration of Haruki's Theorem:
[math]\displaystyle{ \frac{s_1}{s_2} \cdot \frac{s_3}{s_4} \cdot \frac{s_5}{s_6} = 1 }[/math]

Haruki's Theorem says that given three intersecting circles that only intersect each other at two points that the lines connecting the inner intersecting points to the outer satisfy:

[math]\displaystyle{ s_1 \cdot s_3 \cdot s_5 = s_2 \cdot s_4 \cdot s_6 }[/math]

where [math]\displaystyle{ s_1, s_2, s_3, s_4, s_5, s_6 }[/math] are the measure of segments connecting the inner and outer intersection points.[1][2][3]

The theorem is named after the Japanese mathematician Hiroshi Haruki.

References

  1. Wisstein, Eric. "Haruki's Theorem". Wolfram MathWorld. http://mathworld.wolfram.com/HarukisTheorem.html. Retrieved 19 August 2015. 
  2. Bogomolny, Alexander. "Cut the Knot". http://www.cut-the-knot.org/proofs/HarukiTheorem.shtml. Retrieved 19 August 2015. 
  3. Ross Honsberger: Episodes in Nineteenth and Twentieth Century Euclidean Geometry. MAA, 1995, p. 144-146