Create and modify 3D models > Create 2D geometry > Change 2D geometry > Change the radius of a circle
  
Change the radius of a circle
1. Click the circle to change the radius.
2. Click the blue point on the circle.
3. Move the mouse to change the radius of your circle.
4. Click again when the circle has the desired radius. You can also type the radius value and press ENTER.
5. Click OK to complete the operation.
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Select a radius or a diameter dimension and drag the 2D CoPilot to change the radius of an arc or a circle.