The Radius Dimension command
will allow you to dimension the radius of a circle or arc.
To draw a radius dimension:
Select the Radius
Dimension command from the Draw
menu or click on the toolbar icon.
Click a point on an arc or circle.
Drag the mouse to
the desired location for the dimension text and click a second point
to complete the command. A small plus sign (+) will be placed
at the base point of the radius dimension.
Notes:
You can set values for all dimension parts and the
color assignments in the Options command
on the Dimensions tab.
Select the Display
Format and Precision
in the Options command on
the General tab.