Spreadsheet Calculus: Euler's Method

Step 2 Use Euler's method

Here's how Euler's method works. Basically, you start somewhere on your plot. You know what dy/dx or the slope is there (that's what the differential equation tells you.) So you make a small line with the slope given by the equation. Then at the end of that tiny line we repeat the process. Soon enough we've sketched a solution curve to the differential equation. As long as we choose small enough step sizes, the solution curve found this way follows the true solution curve almost perfectly.
Here's how you do it: first set an initial state. In this case I'm going to choose 2, since it's the initial value of the solution curve I sketched earlier. Then, below your initial value you want to type in your differential equation (as a function of the initial value) be sure to multiply it by your dx value. Your differential equation has the form dy/dx. If you multiply it by the step size (dx) then you're left with dy, the change in y, which is added to the previous y value. The picture below explains this a lot better than I ever could.