Derivatives of the Elementary Functions

 

The following table gives the derivatives of all of our elementary functions. All of these are derived from the definition of the derivative. You will not have to derive these formulas but you will have to know them well. We will, of course, have to compute the derivatives of functions that are not elementary. The table in the following lecture will give the rules for this. The derivatives of the elementary functions are fundamental to the entire course.

Derivatives of the Elementary Functions

Elementary Functions

Derivatives

 

You must commit this table to memory.

We could give each of these a name. In order, we will refer to them as the power rule, exponential rule, log rule, sine rule and cosine rule. You should be aware that other authors will have a different list of elementary functions. For example, we could add the other four trig functions to the list. We will see how to get those derivatives from these starting in the next lecture. I am going to focus on the structure of the computations so that you will be able to add whatever you need in the future.

What I want to emphasize in the following lectures is a very important concept referred to in general as analysis. In this context, analysis is applied as follows. We now know the derivatives of the elementary functions. More than likely, the functions that we will need to model real world systems will not be elementary and we will want to know their derivatives - i.e. their rates of change. In a previous lesson we learned how to take a function apart into its elementary pieces. We also kept track of the operations that were used to put these elementary functions together to get the original function. So if we know the derivatives of the elementary functions its reasonable to assume that we can get the derivatives of the more complicated functions from these. That is if we knew how to put the derivatives together to get the derivative of the function that we started with. That process of putting the derivatives together is exactly what we will learn to do in the following lectures. Let me warn you at this point that the derivatives do not necessarily go back together the way that the function came apart. However, once we know which elementary functions are involved and which operations are used we will be able put the derivatives of the elementary functions together in a consistent and well defined way to get the derivative of the function. You will see what this means soon enough.

Right now if you don't understand the previous paragraph, that's okay. But if that's the case after we have been through the next couple of lectures, that's not okay. You will have to review those lectures on taking functions apart and putting them together. I don't mean look at them, I mean study them. You should do all of the homework again. Pay particular attention to composition as this causes the most concern in the computations.

Examples

The formulas for the exponential, log, sine and cosine functions are easy since there is only one possibility for each. The power function has several different flavors. You will sometimes have to do some simple algebra before you can use the power rule.

 

You would do well to add the following two formulas to your memorization list.

The first formula was computed above. The second formula should make perfectly good sense to you. After all, a constant function's values do not change - that's what a constant function is. If its values do not change and the derivative measures the rate of change of the function's values the derivative ought to be zero. Think about it.

 

Homework

Using the above formulas compute the following derivatives.

 

Answers

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