I'm guessing that you are doing this in GSP, and I've done a similar thing in Cabri. I did it in Cabri using a macro and you maybe could do it through a script.
You would need a reference segment from (0,0) to (1,0) which you would use to norm the x-step and the y-step of the segment you wanted the length of. Then construct the segments that are the x-step and the y-step, and fins their lengths in inches or cm, and find the length of the reference segment in the same units. Divide the x- and y-steps by the reference length and use those values with pythagoras to calculate the length of the segment in axes' units. If you can put all of that into a script it will give you what you want - the length of a segment in axes' units.
The construction works in GSP and I have attached a sketch (the built in notation tends the clutter the screen a bit). I guess it depends on whether it can be scripted. Good luck.
Tom De Vries wrote:
> I was trying to create a sketch that would display the rectangular > coordinates of a point and also the polar coordinates of a point. I > must be missing something here, but when I went to display the length > of a line, I found I couldn't express this in "x - y" coordinate > length. I .E. length relative to the coordinate grid. I can get > inches and cm and pixels, but i want the "length" . > > For example, if I have the point with coordinates (3,4) and I measure > the length from (0,0) to (3,4) I would like to get 5 units. > > How would I do this? > > Tom