Help with a lisp routine to add a 12" line to this routine

[Orbytal.edge341183]

;get points to locate centerline of header
         (prompt "\nSelect two points for Rim line: ")
         (command "_.line" pause pause "")
         (setq tmpPnt1 (cdr (assoc 10 (entget (entlast)))))
         (setq tmpPnt2 (cdr (assoc 11 (entget (entlast)))))
         (COMMAND "_.erase" "L" "")
         (setvar "osmode" 0)

         (command "_.line"
                  (polar tmpPnt1 (angle tmpPnt1 tmpPnt2) (* mtScaleFactor 1.25))
                  (polar tmpPnt2 (+ (angle tmpPnt1 tmpPnt2) PI) (* mtScaleFactor 1.25))
                  ""

This part of the lisp draws a line then depending on the dimscale it retracts the 2 ends closer to the center. I was wondering if i could get some help making the lines extend 12" i've tried messing with the scale factors ( IE 1.25 - 1.00 -.25) I seem to be missing something to go in a positive direction versus negative.

Thanks for the help in advance