Tangent function determines slope, gradient or grade of a road, but what about sine?

I'm asking this question because Wikipedia shows a table with slope, gradient and grade calculated by tangent *and* by sine.

The article is here:

Grade (slope) - Wikipedia, the free encyclopedia

and the table is just a short scroll down.

I know slope is always defined as rise over the run so the tangent function is *the* one to use but still, the sine function seems to have its applications.

In the table it says a 45º angle is a 100% grade (by tangent function) but using the sine function it is 70.711%. A 90º angle is a 100% grade when calculated by sine and infinite by the tangent function.

So, I know how to calculate the slope, gradient, grade, etc of a road by the tangent function *and* by the sine function.

However, what are the applications of a *sine function* slope or grade calculation? For example is this used by roofers, mountain climbers, cyclists, etc?