Originally Posted by
david_peterson
Well I think (and I could be wrong here) that the angle in question will vary depening on the size/width of the roof. Generally speaking from a structural stand point, I'd never give the slope. You know the high point and the low point. So you know the x,y & z coords. My answer to this question on a test would be Who Cares; connect the dots.
I guess the answer is still rise over run.
So if your ridge (hp) is centered on the eve end and the eve end is say 24'. So half of the eve end is is 12' wide, you know it's 12' back to the ridge hp. (equal angles have equal opp sides). If you have a 4:12 pitch, you know that the rise on a 12' run is 4'. So you'll still have a 4' rise, now to find the run. To find the run (back to geometery) you need to find the length of c.. Since a^2+b^2=c^2 ; c=the square root of (a^2+b^2). So in the example end up with 16.97'. So your slope is 4:16.97' or the inverse tan of 4/16.97 or 13.26 degrees.
To quote Back To School "I feel like I just gave birth to an accountant".
I hope that help.
If you need more info, let me know. It's complicated, but it's really not that hard once you think about it. You just need to solve for both triangles.