Question

If $$\int {f\left( x \right)dx} = g\left( x \right) + c,$$     then $$\int {{f^{ - 1}}\left( x \right)dx} $$   is equal to :

A. $$x{f^{ - 1}}\left( x \right) + C$$
B. $$f\left( {{g^{ - 1}}\left( x \right)} \right) + C$$
C. $$x{f^{ - 1}}\left( x \right) - g\left( {{f^{ - 1}}\left( x \right)} \right) + C$$  
D. $${g^{ - 1}}\left( x \right) + C$$
Answer :   $$x{f^{ - 1}}\left( x \right) - g\left( {{f^{ - 1}}\left( x \right)} \right) + C$$
Solution :
Let $$I = \int {{f^{ - 1}}\left( x \right)dx} $$     and $${f^{ - 1}}\left( x \right) = t \Rightarrow x = f\left( t \right) \Rightarrow dx = f'\left( t \right)\,dt$$
Put value of $$dx$$  and $${f^{ - 1}}\left( x \right)$$   in $$I,$$ we get $$I = \int {tf'\left( t \right)dt} $$
Now, integrate it by parts, $$I = tf\left( t \right) - \int {f\left( t \right)} dt$$
Given, $$\int {f\left( x \right)dx = g} \left( x \right) + C$$
$$\therefore \,I = tf\left( t \right) - \left[ {g\left( t \right)} \right] + C$$
Now, by putting value of $$t,\,f\left( t \right)$$   and $$g\left( t \right)$$  we get,
$$I = x{f^{ - 1}}\left( x \right)g\left[ {{f^{ - 1}}\left( x \right)} \right] + C$$

Releted MCQ Question on
Calculus >> Indefinite Integration

Releted Question 1

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. $$\sin \,x - 2{\left( {\sin \,x} \right)^{ - 1}} + 5\,{\tan ^{ - 1}}\left( {\sin \,x} \right) + c$$
Releted Question 2

If $$\int_{\sin \,x}^1 {{t^2}f\left( t \right)dt = 1 - \sin \,x} ,$$      then $$f\left( {\frac{1}{{\sqrt 3 }}} \right)$$   is-

A. $$\frac{1}{3}$$
B. $${\frac{1}{{\sqrt 3 }}}$$
C. $$3$$
D. $$\sqrt 3 $$
Releted Question 3

Solve this $$\int {\frac{{{x^2} - 1}}{{{x^3}\sqrt {2{x^4} - 2{x^2} + 1} }}dx} = ?$$

A. $$\frac{{\sqrt {2{x^4} - 2{x^2} + 1} }}{{{x^2}}} + C$$
B. $$\frac{{\sqrt {2{x^4} - 2{x^2} + 1} }}{{{x^3}}} + C$$
C. $$\frac{{\sqrt {2{x^4} - 2{x^2} + 1} }}{x} + C$$
D. $$\frac{{\sqrt {2{x^4} - 2{x^2} + 1} }}{{2{x^2}}} + C$$
Releted Question 4

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. $$\frac{1}{2}\log \left( {\frac{{{e^{4x}} + {e^{2x}} + 1}}{{{e^{4x}} - {e^{2x}} + 1}}} \right) + C$$

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Indefinite Integration


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