Formulas in Foliage (oot an' aboot)

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It is hard to imagine, but the trees we see everywhere in our lives, static though they seem, are constantly moving, constantly growing. They simply grow so slowly that by our perceptions, they look as immobile as stone.
So how do we measure the speed a tree grows? The easiest way is to measure its height at one point in time, then check back later to measure it again. To find the rate of growth you would divide the height it has grown by the time which has elapsed. Put into a formula this is: speed = distance / time. So if a sapling grew 10m in 100 years, its rate of growth would be 1m/year.

But that is an average measurement. What if the tree doesn’t grow at the same pace constantly? What if you wanted to find a tree’s rate of growth at any one instantaneous moment in time?

Then you’d have to measure the growth across an extremely tiny period of time, almost (but not quite) 0 seconds. This is called Δx. As this value tends toward 0, you can approximate the rate of change of growth, using the same formula as before. This process is called differentiation, and is a core tenant of calculus.

— Louis Scott (S6)