Packing $4$ unit circles in an equilateral triangle
OwOUwUOwU, via Wikimedia Commons. CC BY-SA 4.0.
The side length of the smallest equilateral triangle into which $4$ unit circles can be packed.
Value: $4\sqrt{3}$ (≈6.928203)
Updates
-
Upper bound: $4\sqrt{3}$
(≈6.928203)
Reference unknown
[via Circles in Triangles, Erich Friedman] -
1987
Lower bound: $4\sqrt{3}$
(≈6.928203)
Milano in 1987
[via Circles in Triangles, Erich Friedman]