Packing $9$ unit circles in an equilateral triangle
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The side length of the smallest equilateral triangle into which $9$ unit circles can be packed.
Value: $6+2\sqrt{3}$ (≈9.464102)
Updates
-
Upper bound: $6+2\sqrt{3}$
(≈9.464102)
Reference unknown
[via Circles in Triangles, Erich Friedman] -
1993-12
Lower bound: $6+2\sqrt{3}$
(≈9.464102)
Melissen, H. (1993). Densest packings of congruent circles in an equilateral triangle. The American Mathematical Monthly, 100(10), 916-925.
[via Circles in Triangles, Erich Friedman]