Tính tích phân :
\(\int\limits^e_1x^2\ln xdx\)
Tính tích phân :
\(\int\limits^e_1x^3\ln^2xdx\)
Đặt \(u=\ln^2x\rightarrow du=2\ln x\frac{dx}{x},dv=\int\limits x^3dx\rightarrow v=\frac{1}{4}x^4\)
Do đó : \(I=\frac{1}{4}x^4.\ln^2x|^e_1-\frac{1}{4}\int\limits^e_12\ln x.\frac{x^4}{x}dx=\frac{e^4}{4}-\frac{1}{2}\int\limits^e_1x^3\ln sdx=\frac{e^4}{4}-\frac{1}{2}J\left(1\right)\)
Tính \(J=\int\limits^e_1x^3\ln xdx\)
Đặt \(u_1=\ln x\rightarrow du_1=\frac{dx}{x},dv_1=\int x^3dx\rightarrow v_1=\frac{1}{4}x^4\)
Do đó :
\(J=\frac{1}{4}x^4\ln x|^e_1-\frac{1}{4}\int\limits^e_1x^3dx=\frac{e^4}{4}-\frac{1}{16}x^2|^e_1=\frac{3e^4+1}{16}\)
Thay vào (1) ta có :
\(I=\frac{e^4}{4}-\frac{1}{2}\left(\frac{3e^4+1}{16}\right)=\frac{5e^4-1}{32}\)
Tính các tích phân sau bằng phương pháp tính tích phân từng phần :
a) \(\int\limits^{e^4}_1\sqrt{x}\ln xdx\)
b) \(\int\limits^{\dfrac{\pi}{2}}_{\dfrac{\pi}{6}}\dfrac{xdx}{\sin^2x}\)
c) \(\int\limits^{\pi}_0\left(\pi-x\right)\sin xdx\)
d) \(\int\limits^0_{-1}\left(2x+3\right)e^{-x}dx\)
Áp dụng phương pháp tính tích phân, hãy tính các tích phân sau :
a) \(\int\limits^{\dfrac{\pi}{2}}_0x\cos2xdx\)
b) \(\int\limits^{\ln2}_0xe^{-2x}dx\)
c) \(\int\limits^1_0\ln\left(2x+1\right)dx\)
d) \(\int\limits^3_2\left|\ln\left(x-1\right)-\ln\left(x+1\right)\right|dx\)
e) \(\int\limits^2_{\dfrac{1}{2}}\left(1+x-\dfrac{1}{x}\right)e^{x+\dfrac{1}{x}}dx\)
g) \(\int\limits^{\dfrac{\pi}{2}}_0x\cos x\sin^2xdx\)
h) \(\int\limits^1_0\dfrac{xe^x}{\left(1+x\right)^2}dx\)
i) \(\int\limits^e_1\dfrac{1+x\ln x}{x}e^xdx\)
Tính :
a) \(\int\limits^2_{-1}\left(5x^2-x+e^{0,5x}\right)dx\)
b) \(\int\limits^2_{0,5}\left(2\sqrt{x}+\dfrac{3}{x^2}+\cos x\right)dx\)
c) \(\int\limits^2_1\dfrac{dx}{\sqrt{2x+3}}\) (đặt \(t=\sqrt{2x+3}\) )
d) \(\int\limits^2_1\sqrt[3]{3x^3+4}x^2dx\) (đặt \(t=\sqrt[3]{3x^3+4}\) )
e) \(\int\limits^2_{-2}\left(x-2\right)\left|x\right|dx\)
g) \(\int\limits^0_1x\cos xdx\)
h) \(\int\limits^{\dfrac{\pi}{2}}_{\dfrac{\pi}{6}}\dfrac{1+\sin2x+\cos2x}{\sin x+\cos x}dx\)
i) \(\int\limits^{\dfrac{\pi}{2}}_0e^x\sin xdx\)
k) \(\int\limits^e_1x^2\ln^2xdx\)
Sử dụng phương pháp tính tích phân từng phần, hãy tính :
a) \(\int\limits^{\dfrac{\pi}{2}}_0\left(x+1\right)\sin x.dx\)
b) \(\int\limits^e_1x^2lnxdx\)
c) \(\int\limits^1_0ln\left(1+x\right)dx\)
d) \(\int\limits^1_0\left(x^2-2x-1\right)e^{-x}dx\)
Hãy chỉ ra kết quả nào dưới đây đúng :
a) \(\int\limits^{\dfrac{\pi}{2}}_0\sin xdx+\int\limits^{\dfrac{3\pi}{2}}_{\dfrac{\pi}{2}}\sin xdx+\int\limits^{2\pi}_{\dfrac{3\pi}{2}}\sin xdx=0\)
b) \(\int\limits^{\dfrac{\pi}{2}}_0\left(\sqrt[3]{\sin x}-\sqrt[3]{\cos x}\right)dx=0\)
c) \(\int\limits^{\dfrac{1}{2}}_{-\dfrac{1}{2}}\ln\dfrac{1-x}{1+x}dx=0\)
d) \(\int\limits^2_0\left(\dfrac{1}{1+x+x^2+x^3}+1\right)dx=0\)
Tính tích phân : \(I=\int\limits^1_0\left(x-e^{2x}\right)xdx\)
\(I=\int\limits^1_0\left(x+e^{2x}\right)xdx=\int\limits^1_0x^2dx+\int\limits^1_0xe^{2x}dx=I_1+I_2\)
\(I_1=\int\limits^1_0x^2dx=\frac{x^3}{3}|^1_0=\frac{1}{3}\)
Đặt \(\begin{cases}dv=e^{2x}dx\\u=x\end{cases}\) ta có \(\begin{cases}v=\frac{e^{2x}}{2}\\du=dx\end{cases}\)
\(I_2=\frac{xe^{2x}}{2}|^1_0-\int\limits^1_0\frac{e^{2x}}{2}dx=\left(\frac{xe^{2x}}{2}-\frac{e^{2x}}{4}\right)|^1_0=\frac{e^2+1}{4}\)
\(I=I_1+I_2=\frac{e^2+1}{4}+\frac{1}{3}=\frac{3e^2+7}{12}\)
Tính tích phân :
\(\int\limits^2_3\ln\left(x^2-x\right)dx\)
Đặt \(u=\ln\left(x^2-x\right)\rightarrow du=\frac{2x-1}{x^2-x}dx,dv=dx\rightarrow v=x\)
Do đó : \(I=x.\ln\left(x^2-x\right)|^3_2-\int\limits^3_2\frac{x\left(2x-1\right)}{x\left(x-1\right)}dx=3\ln6-2\ln2-\int\limits^3_2\frac{2x-2+1}{x-1}dx\)
\(=\ln54-2\int\limits^3_2dx\frac{d\left(x-1\right)}{x-1}=\ln54-2-\ln\left(x-1\right)|^3_2=3\ln3-2\)
Tính tích phân :
\(\int\limits^e_1\ln^3xdx\)
Đặt \(u=\ln^3x\rightarrow du=3\ln^2x\frac{dx}{x},dv=dx\rightarrow v=x\)
Do đó : \(I=x\ln^3x|^e_1-3\int\limits^3_1\ln^2xdx=e-3J\left(1\right)\)
Tính \(J=\int\limits^e_1\ln^2xdx\)
Đặt \(u_1=\ln^2x\rightarrow du_1=\frac{2\ln x}{x}dx,dv_1=dx\rightarrow v_1=x\)
Do vậy, \(J=x\ln^2x|^e_1-2\int\limits^e_1\ln xdx=e-2\left(x\ln x|^e_1-\int\limits^e_1dx\right)=e-2\left(x\ln x-x\right)|^e_1=e-2\)
Thay vào (1) ta có : \(I=e-3\left(e-2\right)=6-2e\)