Complimentary angles. 90-desired angle =first cut.
This is how we but steep bevels on roof rafters and floor joists using complimentary angles.
The formula is 90 degrees (square) - your target bevel angle = the complimentary angle for your first bevel cut.
So if you need a 70 degree bevel cut, you would subtract 90-70=20. 20 degrees is your first cut, with the short point as your long point measurement for your finish angle.
Now when you square the saw and run it down the short point, it will give you the complimentary angle (70) as your long point.
This was taught to me years ago, custom framing massive waterfront homes that commonly required steep bevels and back cuts for cupolas, sweeps, and irregular hip rafters.
Good tool to have in your brain, much easier than finishing with a hand saw or sawzall, and please. PLEASE don’t tell me to use a chop saw 😂😂🤙