# Using Tables to Find Antiderivatives

## Using Tables to Find Antiderivatives

The inside covers of this book show the patterns for many antiderivatives, and there are reference books which contain many more than the ones here. The table of integrals is to help you now while you are learning calculus and to serve as a reference later when you are using calculus. Think of the tables as a dictionary – something to use when you need to spell a difficult word or need the meaning of a new word. It would be difficult to write a letter if you had to look up the spelling of every word, and it will be difficult to learn and do calculus if you have to look up every antiderivative. Tables of antiderivatives are limited and often take longer to use than finding an antiderivative from scratch, but they can also be very valuable and useful. This section shows how to transform some integrals into forms in the tables and how to use the "recursive" formulas in the tables.

The first examples and practice problems illustrate some of the techniques used to change an integral into a
standard form. **These techniques are useful whether that standard form resides in a table or in your
head**.

**Example 1: **Use the table to find dx.

Solution: Table entry number 35, is the integral pattern of our problem for , so by replacing the with 3 we have .

**Practice 1: **Use the table to find . Notice that a small change in the form of the integrand (from + in the example to – in the practice problem) can lead to a very different looking result.

Sometimes the choice for a constant in the antiderivative pattern appears unusual.

**Example 2: **Use the table to find .

Solution: The table entry 35, , for the first example still works if . Then , .

**Practice 2: **Use the table to find .

Sometimes algebraic manipulations are needed to change the integrand we have into one that exactly
matches the pattern in the table.

**Example 3:** Use the table to find .

Solution: The pattern of this problem is basically an arctangent, but we need to **exactly** match the
pattern in the table. For this problem we can use algebra or change of variables.

**Algebra:** We need rather than , and we can get it by factoring a 4 from each piece of the
denominator: . Then

**Change of variable: **Put . Then , so

**Practice 3:** Use the table to find .

Sometimes we have to change the variable.

**Example 4:** Use the table to find .

Solution: Putting , then so our integrand is transformed:

**Practice 4:** Use the table to find .

How should you recognize whether algebra or a change of variable is needed? Experience and practice, practice, practice.

Source: Dale Hoffman, https://s3.amazonaws.com/saylordotorg-resources/wwwresources/site/wp-content/uploads/2012/12/MA005-5.9-Using-Tables-to-Find-Antiderivatives.pdf

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