半径R=450弦长L=300求弧长C?
弧所对的圆心角为A.
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((300/2)/450)
=38.94度
=38.94*PI/180
=0.679674弧度
C=R*A=450*0.679674=305.85