How can fix the gear inner diameter profile? it showing like hexagonal instead of circle. PFA screenshot for your reference.
You will have to increase the Image quality in your settings.
Go to Settings > Document Properties > Image Quality.
Move the cursor for 'Shaded and draft quality HLR/HLV resolution' between two markers on extreme right. See screenshot below. This will slow down performance of your machine but you will have better image quality and will be able to see nice round and curved shapes.
I resolved the issue, thanks to fatih and salman.
Retrieving data ...