integral of (x+5)^2sin(x)

解答

\int (x + 5)^{2} sin (x) d x

- x^{2} cos (x) + 2 x sin (x) - 10 x cos (x) - 23 cos (x) + 10 sin (x) + C

求解步骤

\int (x + 5)^{2} sin (x) d x

x + 5 = 5 (\frac{x}{5} + 1)

= \int (5 (\frac{x}{5} + 1))^{2} sin (x) d x

化简

(5 (\frac{x}{5} + 1))^{2} sin (x) : x^{2} sin (x) + 10 x sin (x) + 25 sin (x)

= \int x^{2} sin (x) + 10 x sin (x) + 25 sin (x) d x

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

= \int x^{2} sin (x) d x + \int 10 x sin (x) d x + \int 25 sin (x) d x

\int x^{2} sin (x) d x = - x^{2} cos (x) + 2 (x sin (x) + cos (x))

\int 10 x sin (x) d x = 10 (- x cos (x) + sin (x))

\int 25 sin (x) d x = - 25 cos (x)

= - x^{2} cos (x) + 2 (x sin (x) + cos (x)) + 10 (- x cos (x) + sin (x)) - 25 cos (x)

化简

- x^{2} cos (x) + 2 (x sin (x) + cos (x)) + 10 (- x cos (x) + sin (x)) - 25 cos (x) : - x^{2} cos (x) + 2 x sin (x) - 10 x cos (x) - 23 cos (x) + 10 sin (x)

= - x^{2} cos (x) + 2 x sin (x) - 10 x cos (x) - 23 cos (x) + 10 sin (x)

解答补常数

= - x^{2} cos (x) + 2 x sin (x) - 10 x cos (x) - 23 cos (x) + 10 sin (x) + C

\int \frac{t ^{2}}{t ^{2} + 4} d t

\int \frac{1}{3} x^{4} d x

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

\int 5 x^{- 5} d x

\int cos (wt - B z) d t