What is an easy way to estimate seat tube angle? I'm not a Trigonometry guy, but I'm sure there is a simple formula, or I seem to remember that Dan had a chart somewhere in his older fit writings where you could estimate the angle based on your saddle height and the position of the nose of your saddle relative to the Bottom Bracket.

What I'm trying to figure out is, what is my seat tube angle with a saddle height of 81.5cm, with the nose of my saddle (Azoto) even with the bottom bracket? What if I move it 1 cm in front, or maybe 2?

Thanks