I'm sure Glaiel is purposefully making somewhat hyperbolic statements that are not to be taken too literally. Stating how early or late a subject is introduced to students in school could never be a good measure of the difficulty of the subject either way. In this case though, I'm pretty sure basic trigonometric functions are taught somewhere around 8th grade, albeit not very effectively. I recall having stuff about inclined planes taught to us in physics class around the same time we learned about sine and cosine in math.
Ninja chicken pathfinding
Ninja chicken your question doesn't make any sense. You have an extra floor of tiles which you want to link through the stairs. As you said, the stairs node will link to nodes of the upper floor instead of nodes of the same floor. ie: if coordinates [f, i, j] represent a tile on floor f on the ith row and jth column, then a set of stairs on [f, i, j] would link to tiles [f+1, i+1, j], [f+1, i-1, j], [f+1, i, j+1], [f+1, i, j-1] in lieu of the same coordinates on [f, ...] which a regular non-stair tile would link to. It seems to me you answered your own question.
Luis the slope problem is unrelated to ninja chicken's stairs. Ninja chicken is not coding physics, the stairs are just an abstraction for a "transporter" from a node to other nodes.
As far as slopes in games go, the N tutorial covers a lot of very important concepts for coding this kind of things. The other tutorial that was linked merely shows how to displace a character walking up a linear inclination such that he doesn't end up "inside" the ground. Following the instructions of this tutorial results in having a character that moves faster when he's going uphill than when he's walking on flat ground. Not great ...
egg I wouldn't disagree that generally programmers who don't work for big companies are not very good at math. If, however, you claim that the converse is true, ie: that generally programmers who work for big companies are good at "lots and lots of math", then I think we will run into a small disagreement :P