弧长C=12米拱高H=1米计算半径R及两端点间距离L?
Rn+1=(1-(Rn*COS(C/(2*Rn))-Rn+H)/((C/2)*SIN(C/(2*Rn))-H))*Rn
R0=18
R1=17.828
R2=17.831
R3=17.831
R=17.831米
L=2*(R^2-(R-H)^2)^0.5
=2*(17.831^2-(17.831-1)^2)^0.5
=11.775米