已知弦长L=12、弧高H=1.8,半径R=11.672,求圆心角A、面积S、弧长C?
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)
=1.8/2+12^2/(8*1.8)
=10.9
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((12/2)/10.9)
=66.8度
C=PI*R*A/180=PI*10.9*66.8/180=12.708
S=PI*R^2*A/360=PI*10.9^2*66.8/360=69.256