Just a note on circles skirts… if one is using a material that has a lot of bias to it, you may not want to have a perfect cricle. You need to flatten out the hem line or reduce the waist to hem on the bias because it’s going to stretch. Therefore using an arc will not work - need to use splines to accomplish this - refer back to original post. Length of A5-A6 could be as much as an 1" less than A-A1 and A3-A4.
And yes… having cut 1000’s of circle skirts in the last 36 years, I don’t bother with a pattern. A ruler, string (or strip of paper) , pin, marking chalk/pen, and the knowledge of PI is all you need to draw out a skirt.