弦长L=7.4m 半径R=7.42米 求弧长C?
圆心角A=2*ARC SIN((L/2)/R)
=2*ARC SIN((7.4/2)/7.42)
=2*ARC SIN(3.7/7.42)
=59.822度
=59.822*PI/180
=1.04409弧度
弧长C=R*A=7.42*1.04409=7.747米