For an inscribed polygon, the radius of the circle is measured to a vertex between sides of the polygon. 
- Select a tool that allows for an inscribed polygon. For example, click Annotate tab Detail panel Detail panel  (Detail Line). (Detail Line).
 
- Click Modify | Place Lines tab (or respective Modify | Place <Element> tab or Modify | Create <Element> tab) Draw panel Draw panel  (Inscribed Polygon). (Inscribed Polygon).
- On the Options Bar: - Enter the number of sides for the polygon. 
- Optionally, for Offset, specify a value. 
- Optionally, select Radius and specify a value. Note: If you specify a radius, the Offset option is overridden.  
 
- Click in the drawing area to specify the start point. 
- If you have not already specified a radius, move the cursor and click to complete the inscribed polygon. Note: You can also use listening dimensions to enter a value for the radius. After you click in the drawing area to place the inscribed polygon, type the value of the radius and press Enter.