Anyone know a clever formula for calculating the diameter of the rim of a dome/bowl from the diameter of a flat disc - or vice versa? Specifically, if I want to make a small sphere, say 15mm across, from two hemispheres formed by doming two flat discs cut from 0.4 or 0.5mm sheet, how wide should I cut those two discs to start with? I'm sure I could do it by trial and error, but just wondered if anyone knew a way of working it out accurately to begin with.
Alan