已知弧长C和弦长L,求曲率半径R和圆心角A?Rn+1=(1+(L-2*Rn*SIN(C/(2*Rn)))/(L-C*COS(C/(2*Rn))))*Rn取R0,代入上式,得R1,再代入上式,得R2,.直到Rn与Rn-1很接近,就得R=RnA=2*ARC SIN((L/2)/R)度,或者 A=C/R弧度....