Question

求圆台侧面展开图中,扇环所对应的圆心角!已知圆台上下底面半径r,R,和上下地面距离h

Answer 1

如图

h1/(h1+h)=r/R

解h1=hr/(R-r)

OB=根下（h1^2+r^2)=根下{[[hr/(R-r)]^2+r^2}

圆心角（弧度）＝2πr/OB=2πr/根下{[[hr/(R-r)]^2+r^2}