;;求多段线上的弧段(圆或圆弧也有效)的圆心
;;TEST
;;(getCenter (entsel "\n选择多段线弧段: "))

(defun getCenter (EP / E P)
  (mapcar 'set '(E P) EP)
  (setq P (apply 'vlax-curve-getClosestPointTo EP))
  (mapcar '+ P
             (vlax-curve-getsecondderiv
               E
               (vlax-curve-getParamAtPoint E P)
             )
  )
)