知道拱形的弦长为L=3490cm拱高为H=475cm如何求出弧长C是多少?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*R*H+H^2+L^2/42*R*H=H^2+L^2/4R=H/2+L^2/(8*H)=475/2+3490^2/(8*475)=3442.8cmA=2*ARC S...