For Calculus classes.
Use this Excel spreadsheet to show that the integral of f(x) is x dx by specifying x, f(x) and a dx value.
The current f(x) is 1/x, so the integral is ln(x). This shows you that when the integral of 1/x dx is 1, the x value is e.
You can copy the current sheet to another tab and specify your own x, f(x) and dx values to integrate other functions with this numerical method.