Spreadsheet Calculus: Derivatives and Integrals

Step 3 Differentiate it!

Plotting the derivative is relatively easy. A derivative has the form "dy/dx", in other words, the change in y over the change in x. The change in x is easy, and it never changes, it's just what we wrote into cell A2, which in this case is 0.1. The change in y is simply going to be the difference between the cells, which isn't hard to figure out. Type in "=(C2-C1)/$A$2" for cell D2, then drag it down to the bottom (or double click the bottom right of the cell.) The picture should give you a good idea of what to do. There wont be anything in cell D1, by differentiating we lose one of the cells, but if your dx is small enough, it doesn't matter. Make sure to type this into D2 instead of D1, that way when you drag it all the way down the last cell wont display a ridiculously huge number.
Plot this on the same graph as the last one, use the same x values as before. There's your derivative. You can also do the derivative by hand and plot it to make sure that it matches up, it should.
This is helpful if you're having trouble differentiating a function and you want to see what the derivative looks like. Once you get the hang of differentiation though, it gets pretty easy and you wont really need this. Integration on the other hand is quite a bit harder, there are also some functions you wont know how to integrate. Let's do it with spreadsheets!