Question

The integral $$\int\limits_2^4 {\frac{{\log \,{x^2}}}{{\log \,{x^2} + \log \,\left( {36 - 12x + {x^2}} \right)}}} dx,$$       is equal to:

A. $$1$$  
B. $$6$$
C. $$2$$
D. $$4$$
Answer :   $$1$$
Solution :
$$\eqalign{ & I = \int\limits_2^4 {\frac{{\log \,{x^2}}}{{\log \,{x^2} + \log \,\left( {36 - 12x + {x^2}} \right)}}} \cr & I = \int\limits_2^4 {\frac{{\log \,{x^2}}}{{\log \,{x^2} + \log \,{{\left( {6 - x} \right)}^2}}}} .....(1) \cr & I = \int\limits_2^4 {\frac{{\log \,{{\left( {6 - x} \right)}^2}}}{{\log {{\left( {6 - x} \right)}^2} + \log \,{x^2}}}} .....(2) \cr & {\text{Adding (1) and (2), we get}} \cr & 2I = \int\limits_2^4 {dx} = \left[ x \right]_2^4 = 2\,\,\, \Rightarrow I = 1 \cr} $$

Releted MCQ Question on
Calculus >> Definite Integration

Releted Question 1

The value of the definite integral $$\int\limits_0^1 {\left( {1 + {e^{ - {x^2}}}} \right)} \,dx$$     is-

A. $$ - 1$$
B. $$2$$
C. $$1 + {e^{ - 1}}$$
D. none of these
Releted Question 2

Let $$a,\,b,\,c$$   be non-zero real numbers such that $$\int\limits_0^1 {\left( {1 + {{\cos }^8}x} \right)\left( {a{x^2} + bx + c} \right)dx = } \int\limits_0^2 {\left( {1 + {{\cos }^8}x} \right)\left( {a{x^2} + bx + c} \right)dx.} $$
Then the quadratic equation $$a{x^2} + bx + c = 0$$     has-

A. no root in $$\left( {0,\,2} \right)$$
B. at least one root in $$\left( {0,\,2} \right)$$
C. a double root in $$\left( {0,\,2} \right)$$
D. two imaginary roots
Releted Question 3

The value of the integral $$\int\limits_0^{\frac{\pi }{2}} {\frac{{\sqrt {\cot \,x} }}{{\sqrt {\cot \,x} + \sqrt {\tan \,x} }}dx} $$     is-

A. $$\frac{\pi }{4}$$
B. $$\frac{\pi }{2}$$
C. $$\pi $$
D. none of these
Releted Question 4

For any integer $$n$$ the integral $$\int\limits_0^\pi {{e^{{{\cos }^2}x}}} {\cos ^3}\left( {2n + 1} \right)xdx$$     has the value-

A. $$\pi $$
B. $$1$$
C. $$0$$
D. none of these

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