弧长C=835,拱高H=120,求弦长L?
弧半径为R,弧所对的圆心角为A.
Rn+1=(1-(Rn*COS(C/(2*Rn))-Rn+H)/((C/2)*SIN(C/(2*Rn))-H))*Rn
R0=726
R1=704.124
R2=705.312
R3=705.316
R4=705.316
R=705.316
A=C/R=835/705.316=1.1838665弧度=1.1838665*180/π=67.83度
L=2*R*SIN(A/2)
=2*705.316*SIN(67.83/2)
=787.085