To Insert a Dimension for an Arc
1. Click > > 
Dimension. The Select Reference dialog box opens.
Dimension. The Select Reference dialog box opens.2. Select 
on entity, or 
tangent point reference option on the Select Reference dialog box.
on entity, or tangent point reference option on the Select Reference dialog box.3. Select an arc. The ghost image of the dimension appears with the radius format.
4. Right-click and select Diameter, Angular, or Arc Length as the type of the dimension for the arc.