(setq pt3 (polar pt2 (angle pt1 pt2) (/ (distance pt1 pt2) 2)))
Correct me if I'm wrong here, but if you start the polar function from PT2 and pull the angle between PT1 and PT2, you're not going to be at the midpt between PT1 and PT2, but rather that far OFF the end pf PT2. Right???
Shouldn't it be:
(setq pt3 (polar pt1 (angle pt1 pt2) (/ (distance pt1 pt2) 2)))
or:
(setq pt3 (polar pt2 (angle pt2 pt1) (/ (distance pt1 pt2) 2)))
Be nice, remember I'm a lisp hack.