Рисование стрелки под любым углом

CONST PI = 3.141592653#
SCREEN 12
' 30 случайных разнонаправленных стрелок
FOR i = 1 TO 30
  acol = INT(RND(1) * 7) + 7
  lcol = INT(RND(1) * 7) + 7
  x1 = INT(RND(1) * 640)
  x2 = INT(RND(1) * 640)
  y1 = INT(RND(1) * 480)
  y2 = INT(RND(1) * 480)
  CALL DrawArrow(x1, y1, x2, y2, acol, lcol)
NEXT
A$ = INPUT$(1): CLS
SCREEN 0: END

'/////////////////////////////////////////////////////////////////////
' Процедура рисования стрелки
'/////////////////////////////////////////////////////////////////////
SUB DrawArrow (x1, y1, x2, y2, acol, lcol)
  ' Треугольник - стрелка
  dx = x2 - x1
  dy = y2 - y1
  IF dx = 0 THEN A = 90 ELSE A = ATN(dy / dx) * 180 / PI
  IF dx < 0 OR (dx = 0 AND dy < 0) THEN A = 180 + A
  r1 = 4: w = 120: e = 0

  tx1 = (r1 * COS(PI / 180 * (A - e)))
  ty1 = (r1 * SIN(PI / 180 * (A - e)))
  tx2 = (r1 * COS(PI / 180 * (A + w - e)))
  ty2 = (r1 * SIN(PI / 180 * (A + w - e)))
  tx3 = (r1 * COS(PI / 180 * (A - w - e)))
  ty3 = (r1 * SIN(PI / 180 * (A - w - e)))

  LINE (x2 + tx1, y2 + ty1)-(x2 + tx2, y2 + ty2), acol
  LINE (x2 + tx2, y2 + ty2)-(x2 + tx3, y2 + ty3), acol
  LINE (x2 + tx3, y2 + ty3)-(x2 + tx1, y2 + ty1), acol

  PSET (x2 + tx1, y2 + ty1), acol

  LINE (x1, y1)-(x2, y2), lcol
END SUB