The indefinite integral of a rational function can be found if it is first subjected to a partial-fraction decomposition. At worst, the rational function can be expressed as , where (the quotient) is a polynomial that yields to integration by the power rule, and is the remainder. The fraction decomposes to fractions as per Table 6.4.1 in Section 6.4. Table 6.5.1 details the integration of the various partial fractions that the decomposition of generates.
Partial Fraction
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Integration
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Integrates to a logarithm if
Yields to the power rule if
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Complete the square in the denominator.
Set so . Then
Set , and . Then
The last integral yields to the trig substitutions in Table 6.3.1.
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Table 6.5.1 Integrating partial fractions
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Although the examples that follow will illustrate the machinations sketched in Table 6.5.1, this author believes that in this day and age, any reasonable consumer of mathematics will implement the integral of a rational function either with software such as Maple, or at the very least, by the expediency of a table of integrals. This author's table of integrals, in use for more than 50 years, provides the excerpts shown in Table 6.5.2.
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2.
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3.
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4.
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5.
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6.
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Table 6.5.2 Excerpts from a table of integrals
and
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The first three formulas in Table 6.5.2 would be used for the integral of a constant divided by a quadratic; the fourth, for the integral of a constant divided by a power of a quadratic. The fifth formula in Table 6.5.2 would be used for the integral of divided by a quadratic; the sixth, for the integral of divided by a power of a quadratic. Hence, the fourth and sixth formulas in the table are actually reduction formulas.