61.
What is $$\int {\frac{{{e^x}\left( {1 + x} \right)}}{{{{\cos }^2}\left( {x{e^x}} \right)}}dx} $$ equal to ?
Where $$c$$ is a constant of integration.
A
$$x{e^x} + c$$
B
$$\cos \left( {x{e^x}} \right) + c$$
C
$$\tan \left( {x{e^x}} \right) + c$$
D
$$x\,{\text{cosec}}\left( {x{e^x}} \right) + c$$
Answer :
$$\tan \left( {x{e^x}} \right) + c$$
View Solution
Discuss Question
$$\eqalign{
& {\text{Let }}I = \int {\frac{{{e^x}\left( {1 + x} \right)}}{{{{\cos }^2}\left( {x{e^x}} \right)}}dx} \cr
& {\text{Put, }}x{e^x} = t \Rightarrow {e^x}\left( {1 + x} \right)dx = dt \cr
& \therefore \,I = \int {\frac{{dt}}{{{{\cos }^2}t}}} = \int {{{\sec }^2}tdt = } \tan \,t + c = \tan \left( {x{e^x}} \right) + c \cr} $$
where $$'c'$$ is a constant of integration.
62.
If $${l^r}\left( x \right)$$ means $$\log \,\log \,\log .....x,$$ the $$\log $$ being repeated $$r$$ times. Then $${\int {\left\{ {xl\left( x \right){l^2}\left( x \right){l^3}\left( x \right)......{l^r}\left( x \right)} \right\}} ^{ - 1}}dx$$ is equal to :
A
$${l^{r + 1}}\left( x \right) + C$$
B
$$\frac{{{l^{r + 1}}\left( x \right)}}{{r + 1}} + C$$
C
$${l^r}\left( x \right) + C$$
D
None
Answer :
$${l^{r + 1}}\left( x \right) + C$$
View Solution
Discuss Question
Putting $${l^{r + 1}}\left( x \right) = t$$ and $$\frac{1}{{xl\left( x \right){l^2}\left( x \right).....{l^r}\left( x \right)}}dx = dt$$
$$\eqalign{
& {\text{we get, }}\int {\frac{1}{{x{l^2}\left( x \right){l^3}\left( x \right).....{l^r}\left( x \right)}}} \cr
& = \int {1.dt} \cr
& = t + C \cr
& = {l^{r + 1}}\left( x \right) + C \cr} $$
63.
If $$I = \int {{{\sin }^{ - \frac{{11}}{3}}}x\,{{\cos }^{ - \frac{1}{3}}}x\,dx} = A\,{\cot ^{\frac{2}{3}}}x + B\,{\cot ^{\frac{8}{3}}}x + C.$$ Then :
A
$$A = \frac{2}{3},\,B = \frac{8}{3}$$
B
$$A = - \frac{3}{2},\,B = - \frac{3}{8}$$
C
$$A = \frac{3}{2},\,B = \frac{3}{8}$$
D
None of these
Answer :
$$A = - \frac{3}{2},\,B = - \frac{3}{8}$$
View Solution
Discuss Question
$$\eqalign{
& {\text{If,}} \cr
& I = \int {{{\sin }^{ - \frac{{11}}{3}}}x\,{{\cos }^{ - \frac{1}{3}}}x\,dx} , \cr
& {\text{here }}\frac{{ - \frac{{11}}{3} - \frac{1}{3} - 2}}{2} = - 3\,\,\left( {{\text{a negative integer}}} \right) \cr
& I = \int {\frac{{{{\sin }^{ - \frac{{11}}{3}}}x}}{{{{\cos }^{ - \frac{{11}}{3}}}x}}} {\cos ^{ - \frac{1}{3}}}x.{\cos ^{ - \frac{{11}}{3}}}x\,dx \cr
& I = \int {{{\left( {\tan \,x} \right)}^{ - \frac{{11}}{3}}}x.{{\left( {\cos \,x} \right)}^{ - 4}}dx} \cr
& I = \int {{{\left( {\tan \,x} \right)}^{ - \frac{{11}}{3}}}x.{{\sec }^4}xdx} \cr
& I = \int {{{\left( {\tan \,x} \right)}^{ - \frac{{11}}{3}}}\left( {1 + {{\tan }^2}\,x} \right){{\sec }^2}x\,dx} \cr
& {\text{Put }}\tan \,x = t,\,{\sec ^2}x\,dx = dt \cr
& I = \int {{t^{ - \frac{{11}}{3}}}} \left( {1 + {t^2}} \right)dt \cr
& I = \int {\left( {{t^{ - \frac{{11}}{3}}} + {t^{ - \frac{5}{3}}}} \right)} dt \cr
& I = \frac{{{t^{ - \frac{8}{3}}}}}{{ - \frac{8}{3}}} + \frac{{{t^{ - \frac{2}{3}}}}}{{ - \frac{2}{3}}} + C \cr
& I = - \frac{3}{8}{\left( {\tan \,x} \right)^{ - \frac{8}{3}}} - \frac{3}{2}{\left( {\tan \,x} \right)^{ - \frac{2}{3}}} + C \cr
& I = - \frac{3}{2}{\cot ^{\frac{2}{3}}}x - \frac{3}{8}{\cot ^{\frac{8}{3}}}x + C \cr} $$
64.
The value of the integral $$\int {\frac{{{{\cos }^3}x + {{\cos }^5}x}}{{{{\sin }^2}x + {{\sin }^4}x}}dx} $$ is-
A
$$\sin \,x - 6\,{\tan ^{ - 1}}\left( {\sin \,x} \right) + c$$
B
$$\sin \,x - 2{\left( {\sin \,x} \right)^{ - 1}} + c$$
C
$$\sin \,x - 2{\left( {\sin \,x} \right)^{ - 1}} - 6\,{\tan ^{ - 1}}\left( {\sin \,x} \right) + c$$
D
$$\sin \,x - 2{\left( {\sin \,x} \right)^{ - 1}} + 5\,{\tan ^{ - 1}}\left( {\sin \,x} \right) + c$$
Answer :
$$\sin \,x - 2{\left( {\sin \,x} \right)^{ - 1}} - 6\,{\tan ^{ - 1}}\left( {\sin \,x} \right) + c$$
View Solution
Discuss Question
$$\eqalign{
& {\text{Let,}}\,\,\,\,\,I = \int {\frac{{{{\cos }^3}x + {{\cos }^5}x}}{{{{\sin }^2}x + {{\sin }^4}x}}dx} \cr
& = \int {\frac{{\left( {{{\cos }^2}x + {{\cos }^4}x} \right)\cos \,x}}{{{{\sin }^2}x\left( {1 + {{\sin }^2}x} \right)}}dx} \cr
& = \int {\frac{{\left[ {1 - {{\sin }^2}x + {{\left( {1 - {{\sin }^2}x} \right)}^2}} \right]\cos x}}{{{{\sin }^2}x\left( {1 + {{\sin }^2}x} \right)}}dx} \cr
& = \int {\frac{{\left( {2 - 3\,{{\sin }^2}x + {{\sin }^4}x} \right)\cos \,x}}{{{{\sin }^2}x\left( {1 + {{\sin }^2}x} \right)}}dx} \cr
& {\text{Put }}\sin \,x = t\,\,\, \Rightarrow \cos \,x\,dx = dt \cr
& I = \int {\frac{{2 - 3{t^2} + {t^4}}}{{{t^4} + {t^2}}}dt,\,\,\,} I = \int {\left( {1 + \frac{2}{{{t^2}}} - \frac{6}{{{t^2} + 1}}} \right)dt\,} \cr
& = t - \frac{2}{t} - 6\,{\tan ^{ - 1}}\left( t \right) + C \cr
& = \sin \,x - 2{\left( {\sin \,x} \right)^{ - 1}} - 6\,{\tan ^{ - 1}}\left( {\sin \,x} \right) + C \cr} $$
65.
$$\int {\frac{{\left\{ {f\left( x \right).\phi '\left( x \right) - f'\left( x \right).\phi \left( x \right)} \right\}}}{{f\left( x \right).\phi \left( x \right)}}} \left\{ {\log \phi \left( x \right) - \log f\left( x \right)} \right\}dx$$ is equal to :
A
$$\log \frac{{\phi \left( x \right)}}{{f\left( x \right)}} + k$$
B
$$\frac{1}{2}{\left\{ {\log \frac{{\phi \left( x \right)}}{{f\left( x \right)}}} \right\}^2} + k$$
C
$$\frac{{\phi \left( x \right)}}{{f\left( x \right)}}\log \frac{{\phi \left( x \right)}}{{f\left( x \right)}} + k$$
D
none of these
Answer :
$$\frac{1}{2}{\left\{ {\log \frac{{\phi \left( x \right)}}{{f\left( x \right)}}} \right\}^2} + k$$
View Solution
Discuss Question
$$I = \int {\log \frac{{\phi \left( x \right)}}{{f\left( x \right)}}d\left\{ {\log \frac{{\phi \left( x \right)}}{{f\left( x \right)}}} \right\}} = \frac{1}{2}{\left\{ {\log \frac{{\phi \left( x \right)}}{{f\left( x \right)}}} \right\}^2} + k$$
66.
If $$\int {\frac{{dx}}{{f\left( x \right)}}} = \log {\left\{ {f\left( x \right)} \right\}^2} + c,$$ then what is $$f\left( x \right)$$ equal to ?
A
$$2x + \alpha $$
B
$$x + \alpha $$
C
$$\frac{x}{2} + \alpha $$
D
$${x^2} + \alpha $$
Answer :
$$\frac{x}{2} + \alpha $$
View Solution
Discuss Question
We check from the given options one by one. Options (A) and (B) do not satisfy. We check option (C).
$$\eqalign{
& {\text{Let }}f\left( x \right) = \frac{x}{2} + \alpha \cr
& \therefore \,\int {\frac{{dx}}{{\frac{x}{2} + \alpha }}} \cr
& = \int {\frac{{2dx}}{{\left( {x + 2\alpha } \right)}}} \cr
& = 2\,\log \left( {x + 2\alpha } \right) + {c_1} \cr
& = \log {\left( {x + 2\alpha } \right)^2} + {c_1} \cr
& = \log {\left( {\frac{x}{2} + \alpha } \right)^2} + \log \,{2^2} + {c_1} \cr
& = \log {\left( {\frac{x}{2} + \alpha } \right)^2} + c \cr} $$
67.
Let $$I = \int {\frac{{{e^x}}}{{{e^{4x}} + {e^{2x}} + 1}}dx,\,J = \int {\frac{{{e^{ - \,x}}}}{{{e^{ - \,4x}} + {e^{ - \,2x}} + 1}}dx.} } $$
Then for an arbitrary constant $$C,$$ the value of $$J-I$$ equals-
A
$$\frac{1}{2}\log \left( {\frac{{{e^{4x}} - {e^{2x}} + 1}}{{{e^{4x}} + {e^{2x}} + 1}}} \right) + C$$
B
$$\frac{1}{2}\log \left( {\frac{{{e^{2x}} + {e^x} + 1}}{{{e^{2x}} - {e^x} + 1}}} \right) + C$$
C
$$\frac{1}{2}\log \left( {\frac{{{e^{2x}} - {e^x} + 1}}{{{e^{2x}} + {e^x} + 1}}} \right) + C$$
D
$$\frac{1}{2}\log \left( {\frac{{{e^{4x}} + {e^{2x}} + 1}}{{{e^{4x}} - {e^{2x}} + 1}}} \right) + C$$
Answer :
$$\frac{1}{2}\log \left( {\frac{{{e^{2x}} - {e^x} + 1}}{{{e^{2x}} + {e^x} + 1}}} \right) + C$$
View Solution
Discuss Question
$$\eqalign{
& {\text{Given}} \cr
& I = \int {\frac{{{e^x}}}{{{e^{4x}} + {e^{2x}} + 1}}dx,\,\,\,\,} \cr
& J = \int {\frac{{{e^{ - \,x}}}}{{{e^{ - \,4x}} + {e^{ - \,2x}} + 1}}dx} = \int {\frac{{{e^{3x}}}}{{{e^{4x}} + {e^{2x}} + 1}}dx} \cr
& \therefore J - I = \int {\frac{{{e^x}\left( {{e^{2x}} - 1} \right)}}{{{e^{4x}} + {e^{2x}} + 1}}dx} \cr
& {\text{Let }}{e^x} = t\,\, \Rightarrow {e^x}\,dx = dt \cr
& \therefore J - I\int {\frac{{{t^2} - 1}}{{{t^4} + {t^2} + 1}}} dt = \int {\frac{{1 - \frac{1}{{{t^2}}}}}{{{t^2} + 1 + \frac{1}{{{t^2}}}}}dt} \cr
& {\text{Let }}t - \frac{1}{t} = u\,\, \Rightarrow \left( {1 - \frac{1}{{{t^2}}}} \right)dt = du \cr
& \therefore J - I = \int {\frac{{du}}{{{u^2} - 1}} = \frac{1}{2}\log \left| {\frac{{u - 1}}{{u + 1}}} \right| + C} \cr
& = \frac{1}{2}\log \left| {\frac{{\frac{{{t^2} + 1}}{t} - 1}}{{\frac{{{t^2} + 1}}{t} + 1}}} \right| + C \cr
& = \frac{1}{2}\log \left| {\frac{{{e^{2x}} - {e^x} + 1}}{{{e^{2x}} + {e^x} + 1}}} \right| + C \cr} $$
68.
$$\int {\frac{{dx}}{{\cos \,x + \sqrt 3 \,\sin \,x}}} $$ equals-
A
$$\log \,\tan \,\left( {\frac{x}{2} + \frac{\pi }{{12}}} \right) + C$$
B
$$\log \,\tan \,\left( {\frac{x}{2} - \frac{\pi }{{12}}} \right) + C$$
C
$$\frac{1}{2}\log \,\tan \,\left( {\frac{x}{2} + \frac{\pi }{{12}}} \right) + C$$
D
$$\frac{1}{2}\log \,\tan \,\left( {\frac{x}{2} - \frac{\pi }{{12}}} \right) + C$$
Answer :
$$\frac{1}{2}\log \,\tan \,\left( {\frac{x}{2} + \frac{\pi }{{12}}} \right) + C$$
View Solution
Discuss Question
$$\eqalign{
& I = \int {\frac{{dx}}{{\cos \,x + \sqrt 3 \,\sin \,x}}} \cr
& \Rightarrow I = \int {\frac{{dx}}{{2\left[ {\frac{1}{2}\cos \,x + \frac{{\sqrt 3 }}{2}\sin \,x} \right]}}} \cr
& \Rightarrow I = \frac{1}{2}\int {\frac{{dx}}{{\left[ {\sin \frac{\pi }{6}\cos \,x + \cos \frac{\pi }{6}\sin \,x} \right]}}} \cr
& \Rightarrow I = \frac{1}{2}\int {\frac{{dx}}{{\sin \left( {x + \frac{\pi }{6}} \right)}}} \cr
& \Rightarrow I = \frac{1}{2}\int {{\text{cosec}}\,\left( {x + \frac{\pi }{6}} \right)dx} \cr} $$
But we know that $$\int {{\text{cosec}}\,x\,dx} = \log \left| {\left( {\frac{{\tan \,x}}{2}} \right)} \right| + C$$
$$\therefore I = \frac{1}{2}.\log \,\tan \left( {\frac{x}{2} + \frac{\pi }{{12}}} \right) + C$$
69.
$$\int {\frac{{\sqrt x }}{{1 + \root 4 \of {{x^3}} }}dx} $$ is equal to :
A
$$\frac{4}{3}\left[ {1 + {x^{\frac{3}{4}}} + \log \left( {1 + {x^{\frac{3}{4}}}} \right)} \right] + C$$
B
$$\frac{4}{3}\left[ {1 + {x^{\frac{3}{4}}} - \log \left( {1 + {x^{\frac{3}{4}}}} \right)} \right] + C$$
C
$$\frac{4}{3}\left[ {1 - {x^{\frac{3}{4}}} + \log \left( {1 + {x^{\frac{3}{4}}}} \right)} \right] + C$$
D
None of these
Answer :
$$\frac{4}{3}\left[ {1 + {x^{\frac{3}{4}}} - \log \left( {1 + {x^{\frac{3}{4}}}} \right)} \right] + C$$
View Solution
Discuss Question
$$\eqalign{
& {\text{Put }}x = {z^4}\, \Rightarrow dx = 4{z^3}dz \cr
& \therefore \,\int {\frac{{\root 2 \of x }}{{1 + \root 4 \of {{x^3}} }}dx} \cr
& = \int {\frac{{{z^2}.4{z^3}}}{{1 + {z^3}}}dz} \cr
& = 4\int {\frac{{{z^3}.{z^2}}}{{{z^3} + 1}}dz} \cr
& = \frac{4}{3}\int {\frac{{\left( {y - 1} \right)}}{y}dy\,\,\,\,\,\,} \left[ {{\text{Putting }}{z^3} + 1 = y \Rightarrow {z^2}dz = \frac{1}{3}dy} \right] \cr
& = \frac{4}{3}\left( {y - \log \,y} \right) + C \cr
& = \frac{4}{3}\left[ {1 + {x^{\frac{3}{4}}} - \log \left( {1 + {x^{\frac{3}{4}}}} \right)} \right] + C \cr} $$
70.
If $$\int {{{\log }_e}\left( {\sqrt {1 - x} + \sqrt {1 + x} } \right)} dx = x\,{\log _e}\left( {\sqrt {1 - x} + \sqrt {1 + x} } \right) + g\left( x \right) + C.$$
Then $$g\left( x \right) = ?$$
A
$$x - {\sin ^{ - 1}}x$$
B
$${\sin ^{ - 1}}x - x$$
C
$$x + {\sin ^{ - 1}}x$$
D
$${\sin ^{ - 1}}x - {x^2}$$
Answer :
$${\sin ^{ - 1}}x - x$$
View Solution
Discuss Question
$$I = \int {{{\log }_e}\left( {\sqrt {1 - x} + \sqrt {1 + x} } \right)} .1\,dx$$
Integrating by parts taking 1 as the second function.
$$\eqalign{
& I = \log \left( {\sqrt {1 - x} + \sqrt {1 + x} } \right)x - \int {\frac{1}{{\sqrt {1 - x} + \sqrt {1 + x} }}\left[ { - \frac{1}{{2\sqrt {1 - x} }} + \frac{1}{{2\sqrt {1 + x} }}} \right]\left( x \right)dx} \cr
& \,\,\,\,\, = x\,\log \left( {\sqrt {1 - x} + \sqrt {1 + x} } \right) - \frac{1}{2}\int {\frac{{\sqrt {1 - x} - \sqrt {1 + x} }}{{\sqrt {1 - x} + \sqrt {1 + x} }}.\frac{1}{{\sqrt {1 - {x^2}} }}.x\,dx} \cr
& \,\,\,\,\, = x\,\log \left( {\sqrt {1 - x} + \sqrt {1 + x} } \right) - \frac{1}{2}\int {\frac{{\left( {1 - x} \right) + \left( {1 + x} \right) - 2\sqrt {1 - {x^2}} }}{{\left( {1 - x} \right) - \left( {1 + x} \right)}}} .\frac{1}{{\sqrt {1 - {x^2}} }}.x\,dx \cr
& \,\,\,\,\, = x\,\log \left( {\sqrt {1 - x} + \sqrt {1 + x} } \right) - \frac{1}{2}\int {\frac{{\sqrt {1 - {x^2}} - 1}}{{\sqrt {1 - {x^2}} }}} dx \cr
& \,\,\,\,\, = x\,\log \left( {\sqrt {1 - x} + \sqrt {1 + x} } \right) - \frac{1}{2}\left[ {\int {1\,dx - \int {\frac{1}{{\sqrt {1 - {x^2}} }}} } dx} \right] \cr
& \,\,\,\,\, = x\,\log \left( {\sqrt {1 - x} + \sqrt {1 + x} } \right) + \frac{1}{2}\left[ {{{\sin }^{ - 1}}x - x} \right] + C \cr
& \therefore \,f\left( x \right) = x,\,g\left( x \right) = {\sin ^{ - 1}}x - x \cr} $$