Tính tích phân \[I = \mathop \smallint \limits_0^\pi {\cos ^3}x\sin xdx\]

Đặt \[\cos x = t \Rightarrow - \sin xdx = dt \Rightarrow \sin xdx = - dt\]

Đổi cận:\(\left\{ {\begin{array}{*{20}{c}}{x = 0 \Rightarrow t = 1}\\{x = \pi \Rightarrow t = - 1}\end{array}} \right.\)

\( \Rightarrow I = - \int\limits_1^{ - 1} {{t^3}dt = } \int\limits_{ - 1}^1 {{t^3}dt = \frac{{{t^4}}}{4}} \left| {_{ - 1}^1} \right. = \frac{1}{4} - \frac{1}{4} = 0\)

A.\[I = - \mathop \smallint \limits_{\sqrt 2 }^{\frac{2}{{\sqrt 3 }}} \frac{{{t^2}}}{{{t^2} - 1}}dt\]

B. \[I = \mathop \smallint \limits_2^3 \frac{{{t^2}}}{{{t^2} + 1}}dt\]

C. \[I = \mathop \smallint \limits_{\sqrt 2 }^{\frac{2}{{\sqrt 3 }}} \frac{{{t^2}}}{{{t^2} - 1}}dt\]

D. \[I = \mathop \smallint \limits_2^3 \frac{t}{{{t^2} + 1}}dt\]

A.\[ - \frac{2}{3}\]

B. \[4\sqrt 3 - 1\]

C. \[\frac{{2\sqrt 3 }}{3}\]

D. Kết quả khác

A.\[I = 2\mathop \smallint \limits_8^9 \sqrt u du\]

B. \[I = \frac{1}{2}\mathop \smallint \limits_8^9 \sqrt u du\]

C. \[I = \mathop \smallint \limits_9^8 \sqrt u du\]

D. \[I = \mathop \smallint \limits_8^9 \sqrt u du\]

A.\[I = \frac{2}{3}\mathop \smallint \limits_1^2 tdt\]

B. \[I = \frac{2}{3}\mathop \smallint \limits_1^2 {t^2}dt\]

C. \[I = \left( {\frac{2}{9}{t^3} + 2} \right)\left| {_1^2} \right.\]

D. \[I = \frac{{14}}{9}\]

A.\[\mathop \smallint \limits_a^b f'\left( x \right){e^{f\left( x \right)}}dx = 0\]

B.\[\mathop \smallint \limits_a^b f'\left( x \right){e^{f\left( x \right)}}dx = 1\]

C.\[\mathop \smallint \limits_a^b f'\left( x \right){e^{f\left( x \right)}}dx = - 1\]

D. \[\mathop \smallint \limits_a^b f'\left( x \right){e^{f\left( x \right)}}dx = 2\]