1、已知弦長L=12.58米，弦高H=1.48米，求半徑R和弧長C？ 圓心角為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、已知弦長L=11.90米，弦高H=1.18米，求半徑R和弧長C？ 圓心角為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