There are various ways to do that, depending on the exact situation:
- to change the radius or diameter of one or multiple circles to any given value, use the property editor
- to change the radius of a circle in such a way that the circle line goes exactly through an existing reference point (end point, intersection, etc.), drag and drop one of the reference points
- to set the length of an existing line to any given value, use the property editor
- to lengthen or shorten a line in such a way that it exactly meets another entity, use Modify > Trim
- to lengthen or shorten a line using the mouse, drag and drop the end point
- to scale entities by a given factor (e.g. 2.0 or 0.5), use Modify > Scale
Please refer also to our video tutorials at:
1.6 Editing (also covers trimming and drag and drop)
1.7 Property Editor