知道弦长L=2.94,弧高H=0.25,弧长C是多少呀?
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*R*H+H^2+L^2/4
2*R*H=H^2+L^2/4
R=H/2+L^2/(8*H)
=0.25/2+2.94^2/(8*0.25)
=4.4468
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((2.94/2)/4.4468)
=38.6度
=38.6*PI/180
=0.673825弧度
C=R^A=4.4468*0.673825=2.996