弧长是C=24.89,弦长是L=23.49,求半径R?
Rn+1=(1+(L-2*Rn*SIN(C/(2*Rn)))/(L-C*COS(C/(2*Rn))))*Rn
R0=20
R1=21.074
R2=21.236
R3=21.239
R4=21.239
R=21.239