在△ABE和△BCD中,AB = BC ,∠BAE = 60°= ∠CBD ,AE = BD ,
所以,△ABE ≌ △BCD ,
可得：∠ABE = ∠BCD .
∠DOF = ∠CBE+∠BCD = ∠CBE+∠ABE = ∠ABC = 60° .
因为,OF/OD = cos∠DOF = 1/2 ,
所以,OD = 2OF .