Disk covering problem $r(4)$
The smallest value $r(4)$ such that $4$ disks of radius $r(4)$ can be arranged to cover the unit disk.
Value: $\frac{\sqrt{2}}{2}$ (≈0.7071068)
Updates
-
Lower bound: $\frac{\sqrt{2}}{2}$
(≈0.7071068)
Trivial or easy according to the secondary source.
[via Circles Covering Circles, Erich Friedman] -
Upper bound: $\frac{\sqrt{2}}{2}$
(≈0.7071068)
Trivial or easy according to the secondary source.
[via Circles Covering Circles, Erich Friedman]