I have a disturbing problem that has come up while modeling today and I am not sure what to do about it. I drew 2 lines .25" long and then took to more lines essentially extending them to find where they intersected. Then I took the intersection and made that the center of my arc. Then I drew the arc from the ends of each of the .25" lines and tried to join them. But there is this deviation or something. I am not sure what is causing the problem to be honest. here are some pics.

@Ryan14 Are you attempting to join the ends of the arc to the extended lines? If so you can only join lines/curves/arcs at their ends, not a interior points.

What you are seeing is the inaccuracy of the graphics system which is much less precise than the math used in Rhino geometry. Rhino allows unlimited zooming and if you zoom in enough on any geometry there will be apparent gaps. One clue that the gaps are due to the precision of the graphics is when the apparent gaps jump around as zoom level is changed.

Thanks for looking at that for me. I did some more looking and figured out that instead of being 12" long my polysuface was 12.005321" So that made the rest of my reference lines off. Not sure why, but I was able to trim it back and that fixed it. Probably my own mistake.