Question

已知弦长和弦高怎么计算弧长??弦长118,弦高21.

Answer 1

已知弦长和弦高怎么计算弧长C??弦长L=118,弦高H=21.
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)
=21/2+118^2/(8*21)
=93.381
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((118/2)/93.381)
=78.37度
=78.37*PI/180
=1.367799弧度
C=R*A=93.381*1.367799=127.726

Answer 2

不知你这弦高指的是哪一段，设半径为R,则有
R^2-(118/2)^2=(R-21)^2或R^2-(118/2)^2=21^2
自己去算吧