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integral of tan^2(2x)sec^3(2x)

解答

\int tan^{2} (2 x) sec^{3} (2 x) d x

解答

\frac{1}{16} (- sec (2 x) tan (2 x) - ln ∣ tan (2 x) + sec (2 x) ∣ + 2 sec^{4} (2 x) sin (2 x)) + C

求解步骤

\int tan^{2} (2 x) sec^{3} (2 x) d x

使用换元积分法

: \int tan^{2} (u) sec^{3} (u) \frac{1}{2} d u

= \int tan^{2} (u) sec^{3} (u) \frac{1}{2} d u

提出常数:

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

= \frac{1}{2} \cdot \int tan^{2} (u) sec^{3} (u) d u

使用三角恒等式改写

= \frac{1}{2} \cdot \int (- 1 + sec^{2} (u)) sec^{3} (u) d u

乘开

(- 1 + sec^{2} (u)) sec^{3} (u) : - sec^{3} (u) + sec^{5} (u)

= \frac{1}{2} \cdot \int - sec^{3} (u) + sec^{5} (u) d u

使用积分加法定则:

\int f (x) \pm g (x) d x = \int f (x) d x \pm \int g (x) d x

= \frac{1}{2} (- \int sec^{3} (u) d u + \int sec^{5} (u) d u)

\int sec^{3} (u) d u = \frac{1}{2} sec (u) tan (u) + \frac{1}{2} ln ∣ tan (u) + sec (u) ∣

\int sec^{5} (u) d u = \frac{sec ^{4} ( u ) sin ( u )}{4} + \frac{3}{4} (\frac{1}{2} sec (u) tan (u) + \frac{1}{2} ln ∣ tan (u) + sec (u) ∣)

= \frac{1}{2} (- (\frac{1}{2} sec (u) tan (u) + \frac{1}{2} ln ∣ tan (u) + sec (u) ∣) + \frac{sec ^{4} ( u ) sin ( u )}{4} + \frac{3}{4} (\frac{1}{2} sec (u) tan (u) + \frac{1}{2} ln ∣ tan (u) + sec (u) ∣))

u = 2 x

代回

= \frac{1}{2} (- (\frac{1}{2} sec (2 x) tan (2 x) + \frac{1}{2} ln ∣ tan (2 x) + sec (2 x) ∣) + \frac{sec ^{4} ( 2 x ) sin ( 2 x )}{4} + \frac{3}{4} (\frac{1}{2} sec (2 x) tan (2 x) + \frac{1}{2} ln ∣ tan (2 x) + sec (2 x) ∣))

化简

\frac{1}{2} (- (\frac{1}{2} sec (2 x) tan (2 x) + \frac{1}{2} ln ∣ tan (2 x) + sec (2 x) ∣) + \frac{sec ^{4} ( 2 x ) sin ( 2 x )}{4} + \frac{3}{4} (\frac{1}{2} sec (2 x) tan (2 x) + \frac{1}{2} ln ∣ tan (2 x) + sec (2 x) ∣)) : \frac{1}{16} (- sec (2 x) tan (2 x) - ln ∣ tan (2 x) + sec (2 x) ∣ + 2 sec^{4} (2 x) sin (2 x))

= \frac{1}{16} (- sec (2 x) tan (2 x) - ln ∣ tan (2 x) + sec (2 x) ∣ + 2 sec^{4} (2 x) sin (2 x))

解答补常数

= \frac{1}{16} (- sec (2 x) tan (2 x) - ln ∣ tan (2 x) + sec (2 x) ∣ + 2 sec^{4} (2 x) sin (2 x)) + C

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\int sin^{2} (\frac{π x}{8}) d x

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\int x 3 + 2 x d x

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\int (x + 7) e^{0.1 x + 2} d x

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\int (e^{- 5 x} + 7^{x}) d x