Originally Posted by
Elbeinlaw
In an alternate universe, it would seem to me like if you started with practical reality, where percentages were representations of the proportion of a "whole," whatever that is, you'd say that a 100% slope would be 90 degrees--it's the highest a slope can go before it's no longer a slope at all. (And that would make sense in roofing, because a 60% slope would then be something like (just guessing here) 75 degrees.) And a 0% slope would be 0 degrees. That seems to me to be imminently more intuitively sensible.
But for some reason, our forebears decided that practicalities weren't the focus of this datum, it was the arithmatic fraction substituting for the rise/run formulation.
So I wonder why our intellectually giant forebears choose this formulation/
Partly you are still wanting to collapse the different quantities of angle and slope.
Underlying that, however, is the sensible question of why a right angle is 90 degrees. There is a unit called the gradian and a right angle is 100 gradians. You would probably prefer that.
But the Babylonians really liked base 60 math and they left their imprint on how we divide up circles into 360 degrees, rather than 400 gradians (or 2 x pi radians, as is done in SI units and most areas of math).
Besides, 360 is pretty handy because it is highly composite, meaning it can be divided a lot of ways. Same is true for 90 degrees, which can be divided by 1,2,3,5,6,9,10,15,18,30 and 45 (11 distinct ways). 100 can be divided by 1,2,4,5,10,20,25 and 50 (8 distinct ways).
i might have made the case for 120 degrees, which is divisible by 1,2,3,4,5,6,8,10,12,15,20,24,30,40 and 60 (15 ways!). But that was a while ago.
Otto