And this matters...why? Can we measure it on the water? ie, do we say, "Well, we are only at 87 degrees, we'll have to wait another 3 degrees to tack..."

No, we don't. We tack when we think we can make it, and I have no idea exactly what angle that is. When it looks right, I tack. That's why the guys with the most experience do it better than the newbs, they know what looks right.

It's all well and good on a chalkboard, as this college sailor is probably used to being shown, but in reality, who cares exactly what the angle is?

We don't cary enough electronics (like the AC guys do) to make it a worth while number to know, or measure or present that info to us, on board, so what's the point? When it looks good, tack. If it didn't work, tack again.