To Create a Circle in Style
1. Click Style > Curve > Circle. The Circle tab opens.
2. Select the type of circle to create:
Free Curve—Creates a circle that can be moved freely and is not constrained by any geometric entity.
Planar Curve—Creates a circle that lies on the specified plane. By default, the active plane is the reference plane.
3. Click anywhere in the graphics window to place the center of the circle.
4. To change the reference plane, click the Plane or Reference collector on the References tab, and select a new reference plane.
5. To change the radius, type a value in the Radius box, or drag the handle on the circle.
6. If required, drag the center of the circle to change the location of the circle.
7. To maintain the curve shape during edits by moving the free points in proportion to the soft points, click the Options tab, and select the Proportional Update check box.
* 
A curve without proportional update only changes shape at the soft point during edits.
8. Click OK.