Question 154
Let $C$ and $C'$ be two concentric circumferences of radii $r$ and $r'$ respectively. Determine how much the quotient has to be worth $r'/r$ so that in the crown limited by $C$ and $C'$ there are eight circumferences $C_i$, $i=1, \ldots, 8$, which are tangent to $C$ and $C'$, and also that $C_i$ is tangent to $C_{i+1}$ for $i=1, \ldots, 7$ and $C_8$ TANGING TO $C_1$.