Question

The area enclosed between the curve $$y = {\log _e}\left( {x + e} \right)$$    and the coordinate axes is-

A. $$1$$  
B. $$2$$
C. $$3$$
D. $$4$$
Answer :   $$1$$
Solution :
The graph of the curve $$y = {\log _e}\left( {x + e} \right)$$     is as shown in the figure
Application of Integration mcq solution image
$$\eqalign{ & {\text{Required area}}\,{\text{:}} \cr & A = \int\limits_{1 - e}^0 {y\,dx} = \int\limits_{1 - e}^0 {{{\log }_e}\left( {x + e} \right)dx} \cr & {\text{Put}}\,x + e = t\,\, \Rightarrow dx = dt \cr & {\text{Also}}\,x = 1 - e,\,\,t = 1 \cr & {\text{At}}\,x = 0,\,t = e \cr & \therefore A = \int\limits_1^e {{{\log }_e}t\,dt} = \left[ {t\,{{\log }_e}t - t} \right]_1^e \cr & e - e - 0 + 1 = 1 \cr} $$
Hence the required area is 1 square unit.

Releted MCQ Question on
Calculus >> Application of Integration

Releted Question 1

The area bounded by the curves $$y = f\left( x \right),$$   the $$x$$-axis and the ordinates $$x = 1$$  and $$x = b$$  is $$\left( {b - 1} \right)\sin \left( {3b + 4} \right).$$     Then $$f\left( x \right)$$  is-

A. $$\left( {x - 1} \right)\cos \left( {3x + 4} \right)$$
B. $$\sin \,\left( {3x + 4} \right)$$
C. $$\sin \,\left( {3x + 4} \right) + 3\left( {x - 1} \right)\cos \left( {3x + 4} \right)$$
D. none of these
Releted Question 2

The area bounded by the curves $$y = \left| x \right| - 1$$   and $$y = - \left| x \right| + 1$$   is-

A. $$1$$
B. $$2$$
C. $$2\sqrt 2 $$
D. $$4$$
Releted Question 3

The area bounded by the curves $$y = \sqrt x ,\,2y + 3 = x$$    and $$x$$-axis in the 1st quadrant is-

A. $$9$$
B. $$\frac{{27}}{4}$$
C. $$36$$
D. $$18$$
Releted Question 4

The area enclosed between the curves $$y = a{x^2}$$   and $$x = a{y^2}\left( {a > 0} \right)$$    is 1 sq. unit, then the value of $$a$$ is-

A. $$\frac{1}{{\sqrt 3 }}$$
B. $$\frac{1}{2}$$
C. $$1$$
D. $$\frac{1}{3}$$

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