integral of (sin^5(x))/(sqrt(cos(x)))

解答

\int \frac{sin ^{5} ( x )}{cos ( x )} d x

- 2 cos (x) + \frac{4}{5} cos^{\frac{5}{2}} (x) - \frac{2}{9} cos^{\frac{9}{2}} (x) + C

求解步骤

\int \frac{sin ^{5} ( x )}{cos ( x )} d x

使用三角恒等式改写

= \int \frac{( 1 - cos ^{2} ( x ) ) ^{2} sin ( x )}{cos ( x )} d x

使用换元积分法

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

乘开

- \frac{( 1 - u ^{2} ) ^{2}}{u} : - \frac{1}{u} + 2 u^{\frac{3}{2}} - u^{\frac{7}{2}}

= \int - \frac{1}{u} + 2 u^{\frac{3}{2}} - u^{\frac{7}{2}} 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

= - \int \frac{1}{u} d u + \int 2 u^{\frac{3}{2}} d u - \int u^{\frac{7}{2}} d u

\int \frac{1}{u} d u = 2 u

\int 2 u^{\frac{3}{2}} d u = \frac{4}{5} u^{\frac{5}{2}}

\int u^{\frac{7}{2}} d u = \frac{2}{9} u^{\frac{9}{2}}

= - 2 u + \frac{4}{5} u^{\frac{5}{2}} - \frac{2}{9} u^{\frac{9}{2}}

u = cos (x)

代回

= - 2 cos (x) + \frac{4}{5} cos^{\frac{5}{2}} (x) - \frac{2}{9} cos^{\frac{9}{2}} (x)

解答补常数

= - 2 cos (x) + \frac{4}{5} cos^{\frac{5}{2}} (x) - \frac{2}{9} cos^{\frac{9}{2}} (x) + C

d er i v a t i v e y = x

\frac{\partial}{\partial s} (t^{2} - 2 s^{2})

\int 7 t^{8} d t

y^{^{''}} + 2 y^{^{'}} + 2 y = 3 cos (t) - sin (t)

\int_{1}^{3} x e^{- x^{2}} d x