已知弧长为C=4.6,弦长为L=4,求半径R?
Rn+1=(1+(L-2*Rn*SIN(C/(2*Rn)))/(L-C*COS(C/(2*Rn))))*Rn
R0=2
R1=2.329
R2=2.507
R3=2.546
R4=2.547
R5=2.547
半径R=2.547