The third monkey rule tells us how to calculate derivatives of functions that are created by addition or subtraction. See if you can guess it by having Geogebra calculate the derivatives of the two functions below. Use the code snippets:[br][br][code]derivative(f) derivative(g)[/code][br]

As you can see, the derivative of a function which is the sum of two functions is sum of the derivatives of the two functions. Indeed, this is our third monkey rule.[b][br][br]Monkey Rule 3 (AKA "Addition Rule")[/b]: The derivative of a function which is the sum or difference of two functions is the sum or difference of the derivatives of the two functions.