1、已知弦长L=12.58米,弦高H=1.48米,求半径R和弧长C?
圆心角为A.
R^2=(R-H)^2+(L/2)^2
R^2=R^2-2*R*H+H^2+L^2/4
2*R*H=H^2+L^2/4
R=H/2+L^2/(8*H)
=1.48/2+12.58^2/(8*1.48)
=14.106米
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((12.58/2)/14.106)
=52.96度
=52.96*PI/180
=0.92436弧度
C=A*R
=0.92436*14.106
=13.039米

2、已知弦长L=11.90米,弦高H=1.18米,求半径R和弧长C?
圆心角为A.
R=H/2+L^2/(8*H)
=1.18/2+11.9^2/(8*1.18)
=15.591米
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((11.9/2)/15.591)
=44.87度
=44.87*PI/180
=0.78312弧度
C=A*R
=0.78312*15.591
=12.21米