Disk covering problem $r(12)$
The smallest value $r(12)$ such that $12$ disks of radius $r(12)$ can be arranged to cover the unit disk.
Lower bound:
Unknown
Upper bound:
${\approx}0.361141$
Updates
-
1997
Upper bound: ${\approx}0.361141$
Hans Melissen in 1997
[via Circles Covering Circles, Erich Friedman]