I have these perfect laser-cut acrylic templates to make this Rose Dream quilt block (for a 6" block). Now I need to create illustrated instructions to make the block from fabric. Been doing this for years, so the instructions are not the issue. I created the block quickly in CD, no problem. However, when I checked it against the acrylic template, the arcs of the lens-shaped piece did not match. Took me awhile to understand that the creator made the template a specific width, so it's not a 90° arc.
So...the challenge is to create the block so that with of the arc is 2.00" (that would make the height of the arc 1.00"). If you're bored or curious to try, I've attached a PDF with a few more details. BTW, I think I found a way to do it, but I'm curious to see if someone comes up with another way. Just keep in mind...all the geometry I know, I've learned as a quilter. My hubby told be this is really trigonometry. RoseDream_challenge.pdf
If you want to do this as a true circular arc, then you could look up information on calculating the "chord length" of a circle.
There are also some on-line calculators. When I use this one - planetcalc.com - circular segment , using the "Segment defined by chord and height" - then I get a radius of 2.75".
Here's a comparison of curves created by the two methods I described: