Lester's theorem

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Short description: Several points associated with a scalene triangle lie on the same circle
The Fermat points [math]\displaystyle{ X_{13},X_{14} }[/math], the center [math]\displaystyle{ X_5 }[/math] of the nine-point circle (light blue), and the circumcenter [math]\displaystyle{ X_3 }[/math] of the green triangle lie on the Lester circle (black).

In Euclidean plane geometry, Lester's theorem states that in any scalene triangle, the two Fermat points, the nine-point center, and the circumcenter lie on the same circle. The result is named after June Lester, who published it in 1997,[1] and the circle through these points was called the Lester circle by Clark Kimberling.[2] Lester proved the result by using the properties of complex numbers; subsequent authors have given elementary proofs[3][4][5][6], proofs using vector arithmetic,[7] and computerized proofs.[8]

See also

References

  1. Lester, June A. (1997), "Triangles. III. Complex triangle functions", Aequationes Mathematicae 53 (1–2): 4–35, doi:10.1007/BF02215963 
  2. "Lester circle", The Mathematics Teacher 89 (1): 26, 1996 
  3. Shail, Ron (2001), "A proof of Lester's theorem", The Mathematical Gazette 85 (503): 226–232, doi:10.2307/3622007 
  4. Rigby, John (2003), "A simple proof of Lester's theorem", The Mathematical Gazette 87 (510): 444–452, doi:10.1017/S0025557200173620 
  5. Scott, J. A. (2003), "Two more proofs of Lester's theorem", The Mathematical Gazette 87 (510): 553–566, doi:10.1017/S0025557200173917 
  6. Duff, Michael (2005), "A short projective proof of Lester's theorem", The Mathematical Gazette 89 (516): 505–506, doi:10.1017/S0025557200178581 
  7. Dolan, Stan (2007), "Man versus computer", The Mathematical Gazette 91 (522): 469–480, doi:10.1017/S0025557200182117 
  8. Trott, Michael (1997), "Applying GroebnerBasis to three problems in geometry", Mathematica in Education and Research 6 (1): 15–28, http://library.wolfram.com/infocenter/Articles/1754/ 

External links