关键词:
Three circles CaC_{a}Ca, CbC_{b}Cb, and CcC_{c}Cc, all with radius RRR and tangent to each other, are located in two-dimensional space as shown in Figure 111. A smaller circle C1C_{1}C1 with radius R1R_{1}R1 (R1<RR_{1}<RR1<R) is then inserted into the blank area bounded by CaC_{a}Ca, CbC_{b}Cb, and CcC_{c}Cc so that C1C_{1}C1 is tangent to the three outer circles, CaC_{a}Ca, CbC_{b}Cb, and CcC_{c}Cc. Now, we keep inserting a number of smaller and smaller circles Ck (2≤k≤N)C_{k}\ (2 \leq k \leq N)Ck (2≤k≤N) with the corresponding radius