I am not being ironic. My point was that, although this formula may be correct and very helpful, at some point the dimensions that are calculated need to be transferred to the materials being cut. So the idea that maths is more accurate than a pencil line becomes irrelevant.
Personally, I like to draw things out in CAD. I know other people do things different ways and people find ways of working that suit them individually.
I do not know if your formula works, I would never use it even if it did, but that is just my opinion and my preference for the way I work. I would rather 'see' how parts fit together than figure out numbers that, theoretically, make it all work
I am not being critical of you posting ideas and calculations, it would be a sad day if people stop doing that