Is it a way to digitize indicating a curve (colored on a white or black or different colour background) from point to point ? I think i've been told that, but i don't KNOW to do it ! Please consider a quite low GIS knowleadge....(sorry)
You can do the curve between two lines
The points you mention are the 'Tangent Points'
Use the fillet tool in the Advanced Editing toolbar in ArcGIS 9.3
You can fix the radius of the curve in the fillet options