弓形弦长是L=86 高是H=7 求弧长C是多少啊?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)=7/2+86^2/(8*7)=135.571A=2*ARC SIN((L/2)/R)=2*ARC SIN((86/2)/...