(defun c:alint ();arclineinters (lp1 lp2 rpt vp1 vp2 / )
  (setq line_sel (entsel "\nSelect line")
	line_ent (entget (car line_sel))
	lp1 (cdr (assoc 10 line_ent))
	lp2 (cdr (assoc 11 line_ent))
	circ_sel (entsel "\nSelect Circle")
	circ_ent (entget (car circ_sel))
	rpt (cdr (assoc 10 circ_ent))
	arcrad (cdr (assoc 40 circ_ent))
  )
  (setq
;;;     curextmax (getvar "extmax")
;;;	curextmin (getvar "extmin")
;;;	curxdist (-(car curextmax)(car curextmin))
;;;	curydist (-(cadr curextmax)(cadr curextmin))
;;;	arcrad (distance rpt vp1)
	trig_lc_a (distance lp1 lp2)
	trig_lc_b (distance rpt lp2)
	trig_lc_c (distance rpt lp1)
	trig_lc_s (/(+ trig_lc_a trig_lc_b trig_lc_c)2.0)
	trig_uc_K (sqrt(/(*(- trig_lc_s trig_lc_a)(- trig_lc_s trig_lc_b)(- trig_lc_s trig_lc_c))trig_lc_s))
	trig_uc_A (* 2.0 (atan(/ trig_uc_K (- trig_lc_s trig_lc_a))))
	trig_uc_B (* 2.0 (atan(/ trig_uc_K (- trig_lc_s trig_lc_b))))
	trig_uc_C (* 2.0 (atan(/ trig_uc_K (- trig_lc_s trig_lc_c))))
  )
  (cond
     ((or;arc intersection is possible if...
       (and ;both ends of line lie on circle
	  (eq (distance rpt lp1) arcrad)
	  (eq (distance rpt lp2) arcrad)
	)
       (or ;one end of line lies on circle
	  (eq (distance rpt lp1) arcrad)
	  (eq (distance rpt lp2) arcrad)
	)
       (or ;One end of line is inside circle and one end of line is outside circle
	  (and(<(distance rpt lp1) arcrad)(>(distance rpt lp2) arcrad))
	  (and(>(distance rpt lp1) arcrad)(<(distance rpt lp2) arcrad))
	)
       (and ;both ends lie outside circle but height of triangle with line as base <= radius
	   (< trig_uc_B (/ PI 2.0));angle B < 90°
	   (< trig_uc_C (/ PI 2.0));angle C < 90°
	   (> trig_lc_c arcrad);distance from rpt to angle B apex <= arc radius
	   (> trig_lc_b arcrad);distance from rpt to angle C apex >= arc radius
	   (<= (* trig_lc_c (cos (- (/ PI 2.0) trig_uc_B))) arcrad)
	 )
       )
      (PRINC "\nOK, an intersection is possible... ")
      (PRINC)
    )
  )
)