圆弧计算：弦长10.52m,84m,求弧长?弦长3m,84m,求弧长?

弦长L=10.52m,弦高H=12.84m,求弧长C?
弧半径为R,弧所对的圆心角为A.
R^2=(R-H)^2+(L/2)^2
R^2=R^2-2*H*R+H^2+L^2/4
2*H*R=H^2+L^2/4
R=H/2+L^2/(8*H)
=12.84/2+10.52^2/(8*12.84)
=7.497m
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((10.52/2)/7.497)
=89.107度
C=PI*R*(360-A)/180=PI*7.497*(360-89.107)/180=35.446m
弦长L=3m,弦高H=11.84m,求弧长C?
弧半径为R,弧所对的圆心角为A.
R^2=(R-H)^2+(L/2)^2
R^2=R^2-2*H*R+H^2+L^2/4
2*H*R=H^2+L^2/4
R=H/2+L^2/(8*H)
=11.84/2+3^2/(8*11.84)
=6.015m
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((3/2)/6.015)
=28.881度
C=PI*R*(360-A)/180=PI*6.015*(360-28.881)/180=34.761m为什么同样的题你今天算的和前天你算的差那么多，这个对我很重要的弦长L=10.52m，弦高H=12.84m，求弧长C？弧半径为R，弧所对的圆心角为A。R^2=(R-H)^2+(L/2)^2R^2=R^2-2*H*R+H^2+L^2/42*H*R=H^2+L^2/4R=H/2+L^2/(8*H)=12.84/2+10.52^2/(8*12.84)=7.497mA=2*ARC SIN((L/2)/R)=2*ARC SIN((10.52/2)/7.497)=89.107度C=PI*R*(360-A)/180=PI*7.497*(360-89.107)/180=35.446mH=R+R*COS(A/2)=7.497+7.497*COS(89.107/2)=12.84m弦长L=3m,弦高H=11.84m，求弧长C？弧半径为R，弧所对的圆心角为A。R^2=(R-H)^2+(L/2)^2R^2=R^2-2*H*R+H^2+L^2/42*H*R=H^2+L^2/4R=H/2+L^2/(8*H)=11.84/2+3^2/(8*11.84)=6.015mA=2*ARC SIN((L/2)/R)=2*ARC SIN((3/2)/6.015)=28.881度C=PI*R*(360-A)/180=PI*6.015*(360-28.881)/180=34.761mH=R+R*COS(A/2)=6.015+6.015*COS(28.881/2)=11.81m 应该今天算的是对的！呵呵L=2πRn/360°=πRn/180我代入公式进去不对，好像前些天是对的！我晕了，你有没有晕了若R>H，则：C=PI*R*A/180若R