No. When you first start learning about derivatives, you are told you draw a line tangent to a point and then find the slope of that line at that point. The slope is just del y / del x. So, if del x = 1, then the slope is just del y / 1 = del y = the height of the triangle.

Of course, it is more useful to get a derivative as a function of x, so you don't have to do this at every point. But, as a starting point, when you are first learning about derivatives and only have a background in algebra and geometry, this is a nice way to think about it.