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12th Grade > Mathematics

INDEFINITE INTEGRATION MCQs

Total Questions : 30 | Page 2 of 3 pages
Question 11. dx(x3)(4/5)(x+1)6/5=
  1.    ((x−3)(x+1)(1/5))+c
  2.    54(x−3x+1)1/5+c
  3.    (x−3x+1)1/5+c
  4.    (x−3)6/5(x+1)4/5+c
 Discuss Question
Answer: Option B. -> 54(x−3x+1)1/5+c
:
B
I=dx(x3)4/5(x+1)6/5Putt=x3x+1dt=4(x+1)2dx.I=14dtt4/5=14(t4/5+14/5+1)=54t1/5=54(x3x+1)1/5
Question 12. The anti – derivative of the function (3x + 4) |sin x|, when 0<x<π, is given by
  1.    3 sin x−(3x+4) cos x+c
  2.    3 sin x+(3x+4) cos x+c
  3.    −3 sin x−(3x+4) cos x+c
  4.    None of these
 Discuss Question
Answer: Option A. -> 3 sin x−(3x+4) cos x+c
:
A
In the interval (0,π), sin x is positive, therefore, (3x+4)|sinx|=(3x+4)sinx.
The antiderivative of (3x+4)|sinx| is
=(3x+4)sinxdx=(3x+4)cosx+3cosxdx=(3x+4)cosx+3sinx+c
Question 13. 17 cos2xsin7xcos2xdx=f(x)(sinx)7+C, then f(x) is equal to
  1.    sin x
  2.    cos x
  3.    tan x
  4.    cot x
 Discuss Question
Answer: Option C. -> tan x
:
C
17cos2xsin7xcos2xdx=(sec2xsin7x7sin7x)dx=sec2xsin7xdx7sin7dx=I1+I2Now,I1=sec2xsin7dx=tanxsin7x+7tanxcosxsin8x=tanxsin7xI2I1+I2=tanxsin7x+Cf(x)=tanx
Question 14. If In=tannxdx,then I0+I1+2(I2+...I8)+I9+I10, is equal to
  1.    ∑9n=1tannxn
  2.    1+∑8n=1tannxn
  3.    ∑9n=1tannxn+1
  4.    ∑10n=2tannxn+1
 Discuss Question
Answer: Option A. -> ∑9n=1tannxn
:
A
We have In=tannxdx=tann2x(sec2x1)dx=tann1xn1In2i.e.In2+In=tann1xn1(n2)
Thus, we have
I0+I1+2(I2+....+I8)+I9+I10=(I0+I2)+(I1+I3)+(I2+I4)+(I3+I5)+(I4+I6)+(I5+I7)+(I6+I8)+(I7+I9)+(I8+I10).=10n=2tann1xn1=9n=1tannxn
Question 15. Primitive of f(x)=x.2In(x2+1) with respect to x  is
  1.    2In(x2+1)(x2+1)+C
  2.    (x2+1)2In(x2+1)In2+1+C
  3.    (x2+1)In2+12(In2+1)+C
  4.    (x2+1)In22(In2+1)+C
 Discuss Question
Answer: Option C. -> (x2+1)In2+12(In2+1)+C
:
C
I=x2In(x2+1)dx let x2+1=t;xdx=dt2
Hence I=122Intdt=12tIn2dt=12.tIn2+1In2+1+C=12.(x2+1)In2+1In2+1+C
Question 16. x{f(x2)g′′(x2)f′′(x2)g(x2)}dx
  1.    f(x2)g′(x2)−g(x2)f′(x2)+c
  2.    12{f(x2)g(x2)f′(x2)}+c
  3.    12{f(x2) g′(x2)−g(x2) f′(x2)}+c
  4.    None of these
 Discuss Question
Answer: Option C. -> 12{f(x2) g′(x2)−g(x2) f′(x2)}+c
:
C
Put x2=tI=12{f(t)g′′(t)g(t)f′′(t)}dt=12{f(t)g(t)f(t)g(t)g(t)f(t)+g(t)f(t)dt}+cI=12{f(t)g(t)g(t)f(t)}+c=12{f(x2)g(x2)g(x2)f(x2)}+c
Question 17. If (x1x+1)dxx3+x2+x=2tan1f(x)+C, find f(x).
  1.    x+1x+1
  2.    x+1x+2
  3.    x−1x+1
  4.    x−1x−1
 Discuss Question
Answer: Option A. -> x+1x+1
:
A
I=(x1)dx(x+1)xx+1+1x=(x1)(x+1)dx(x+1)2xx+1+1x=(11x2)dx(x+1x+2)x+1x+1Putx+1+1x=t2(11x2)dx=2tdt=2tdt(t2+1)t=2tan1t+c=2tan1(x+1x+1)+c
f(x) = x+1x+1
Question 18. Let f(x)=2sin2x1cosx+cosx(2sinx+1)1+sinx then ex(f(x)+f(x))dx equals
(where c is the constant of integeration)
  1.    extanx+c
  2.    excotx+c
  3.    excosec2x+c
  4.    None of these
 Discuss Question
Answer: Option A. -> extanx+c
:
A
cosx(1+2sinx)1+sinxcos2xsin2xcosx=cos2x(1+2sinx)(1+sinx)(cos2xsin2x)cosx(1+sinx)
=sinxcos2x+sin2x(1+sinx)cosx(1+sinx)=sinx(1sinx)+sin2xcosx=tanx
Question 19. (2+sec x)sec x(1+2sec x)2dx
  1.    12cosec x+cot x+C
  2.    2cosec x+cot x+C
  3.    12cosec x−cot x+C
  4.    2cosec x−cot x+C  
 Discuss Question
Answer: Option A. -> 12cosec x+cot x+C
:
A
(2cosx+1)(2+cosx)2dx=(2+cosx)cosx+sin2x(2+cosx)2dx=cosx2+cosxdxsin2x(2+cosx)2dx=sinx2+cosx+c
Question 20. (1+tanx)(1+tan2x)2tanxdx equal to 
  1.    logtan2x+√tanx+c  
  2.    logtan2x+12√tanx+c  
  3.    log|tanx|+2√tanx+c  
  4.    log|tanx|+√tanx+c
 Discuss Question
Answer: Option A. -> logtan2x+√tanx+c  
:
A
12sinxcosxdx+12tanxsinxcosxdx=12sin2x+cos2xsinxcosxdx+12sec2xtanxdx=log(tan2x)+tanx+c

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