Let’s say you wanted to figure out angles based on a desired arc length and radius, the math is nasty.
Alternately, you can go here:
Yeet! Angles everywhere.
Alternately, for a given angle and radius you can determine the arc length.
It’s highly specialized, but it sure helped me out for this really specific thing I am doing. I haven’t explored, but they have a lot of other calculators. Let’s see… Oh wow, there are a lot. You’ll just have to poke around.