Why the Inkscape circle drawing automatically draw a quarter circle instead of the whole circle?
Inkscape will remember the last configuration for creating a circle. If you look on the toolbar after selecting or creating a circle, you'll see three icons, one for closed arc:
one for open arc:
and finally, full circle.
If circle is previously selected, and you wish to create an arc, click and change the start or end values to "activate" the other two icons. Clicking full circle icon grays out the three icons.
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