弦長(zhǎng)L=15米,弦中心到弧頂H=3米2,求弧長(zhǎng)C和R?
弧所對(duì)的圓心角為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)
=3.2/2+15^2/(8*3.2)
=10.389米
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((15/2)/10.389)
=92.4253度
=92.4253*PI/180
=1.61313弧度
C=A*R=1.61313*10.389=16.759米