Question 32767
Slope is a tricky definition. Think of it as steepness. Think of a steep roof
If it's steep, we say the slope is large. For a roof to be steep, the y
has to be greater than the x. So the slope is y/x 
y/x is the tangent of the angle of inclination. 
If the problem says 1/13 is the slope, tan a = 1/13
where a is the angle.
1/13 = .0769
a = the angle whose tangent is .0769. This is written as
a = tan(-1) .0769
I get 4.399 degrees