I'm not smart enough to do trig either, but my calculator is. Spreadsheets work fine and are convenient, though, as long as they have the correct formula. Any popular spreadsheet should be correct.
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That Excel file looks like the beginnings of the file you started for me, Bob. Way back when I wanted to keep this info and measure. I still have the same Spreadsheet you sent me, although it has changed many times. It still does that math for me and I use "IT only" for my calculations.
A quick and dirty is; spine thickness/active width x 57.3.
If the geometry is going to yield different bevel angles along the edge I go by the most acute spot as that is the limit that I'm generally pushing.
Good job Victor and in less than 50 words