Why do circles have cusp joins?

[gwpriester]

Fascinating, Acorn. I'm off to try this.

OK, I'm back.

Concert to Editable Shapes and press C, does not work for me in Designer Pro+. Nor does pressing the Cusp icon on the Infobar.

Creating a circle with no modifications, using the Radius Creation option and creating a circle from a square and making both the same size: 250px and then center aligning both and zooming in 300% does not show any noticeable difference.