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受欢迎的微积分 >

integral of 1/((x^2+a))

解答

\int \frac{1}{( x ^{2} + a )} d x

解答

\frac{1}{a} arctan (\frac{1}{a} x) + C

求解步骤

\int \frac{1}{x ^{2} + a} d x

x^{2} + a = a (\frac{x ^{2}}{a} + 1)

= \int \frac{1}{a ( \frac{x ^{2}}{a} + 1 )} d x

提出常数:

\int a \cdot f (x) d x = a \cdot \int f (x) d x

= \frac{1}{a} \cdot \int \frac{1}{\frac{x ^{2}}{a} + 1} d x

使用换元积分法

= \frac{1}{a} \cdot \int \frac{a}{u ^{2} + 1} d u

提出常数:

\int a \cdot f (x) d x = a \cdot \int f (x) d x

= \frac{1}{a} a \cdot \int \frac{1}{u ^{2} + 1} d u

使用积分常见定则:

\int \frac{1}{u ^{2} + 1} d u = arctan (u)

= \frac{1}{a} a arctan (u)

u = \frac{1}{a} x

代回

= \frac{1}{a} a arctan (\frac{1}{a} x)

化简

\frac{1}{a} a arctan (\frac{1}{a} x) : \frac{1}{a} arctan (\frac{1}{a} x)

= \frac{1}{a} arctan (\frac{1}{a} x)

解答补常数

= \frac{1}{a} arctan (\frac{1}{a} x) + C

作图

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