Take a circle, divide into 5, remove the unwanted edges, add an empty, parent, rotate by 72 degrees and add an array linked to the empty and you have a circle in 5 segments.
However, extruding and scaling becomes a real hassle. The only way you can E+S the entire circumference is to have the Pivot set as Cursor and make sure the cursor is always central. However, this isn’t a load of good when you want to move the cursor around for fine detail, and sizing away from the baseline is always a problem.
How do you get around this problem so a segment behaves as the full circle?
For the same matter, how would you achieve this with a mirror modifier?
The only reason a default circle, in edit mode, scales on its center is because that’s the median point of the vertices. Blender doesn’t recognize circles, so its kind of silly to expect it to recognize an arc, then treat it as a circles. If you want, duplicate a vertex and place it at the center, then select it last and use the active element pivot point.
Correct me if I’m wrong, but I think I understand your problem. After deleting most of a circle, you only want to rotate/scale/transform/copy only one arc segment of a circle as though the entire circle was still there. While I’m sure there is a more reliable but technically difficult solution, here are two that I regularly use:
I think I understand your methodology you mentioned here: when you create the circle, before you do anything else, press “Ctrl+S” and select the option “Cursor to Selected.” Then, near the bottom of the screen, click the “Pivot center” menu and select “3D Cursor.” Now when you scale the arc, its rotating/scaling/array/etc will take place from the 3D cursor rather than the median point of the arc vertices, and the 3D cursor will be in the same place as the center of the original circle after you delete your vertices.
For if you’ve already deleted most of the circle, which sounds more like what you’re talking about:
Near the bottom of the screen, just above the timeline but in the middle of the toolbar, click on the “Transformation Orientation” menu and select “Normal.” Right next to that, click on the “Pivot center” menu and select “Individual Origins.” Now, in edit mode, select any two vertices of the arc you’ve created that aren’t immediately connected.
Then, press “e” to extrude the vertices along their local normals (press “z” twice after hitting “e” to extrude if it does not automatically do this) but only extrude them to a length exactly equal to the radius of the old circle (which would be only 1 unit for the default circle) by simply typing the number of units in the central screen.
Then, select both central intersecting vertices (they should still be selected if you didn’t do anything else) and hit “Alt+M”, and select “Merge at center” and the two vertices will then merge where the center of the original circle use to be and you will not have a wedge.
Now, select the new central vertex you’ve just created (which should still be selected if nothing else was done) and then, in the “Pivot center” menu, select “Active Element.” Select all vertices of the arc/wedge and then select the new central vertex last. When you go to rotate/scale/ect the arc, it will scale from the new central vertex which is the currently active element. You can also use the same 3D cursor technique at this point to move the 3D cursor to the new central vertex.
If you don’t know the radius of the original circle, you can extrude the vertices until a little bit past where they intersect.
In the user preferences, enable an addon called “dynamic spacebar menu” and save the settings.
In edit mode, select the edges that contain the intersection, hit the spacebar and type “cursor to edge intersection.”
Then, using the same technique you already know with moving the 3D cursor and setting it as the pivot, you can now scale the arc as though the circle was still there and delete the unwanted edges or add an empty at the cursor and use it as the center for an array modifier.