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12th Grade > Mathematics

INTEGRALS MCQs

Total Questions : 30 | Page 2 of 3 pages
Question 11. sin3x(cos4x+3cos2x+1)tan1(secx+cosx)dx=
  1.    tan−1(secx+cosx)+c
  2.    log|tan−1(secx+cosx)|+c
  3.    1(secx+cos2x)2+c
  4.    log|secx+cosx|+c
 Discuss Question
Answer: Option B. -> log|tan−1(secx+cosx)|+c
:
B
Put tan1(secx+cosx)=f(x)f1(x)=sin3xcos4x+3cos2x+1f1(x)f(x)=log|f(x)|+c
Question 12. 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 13. If cos 8x+1tan 2xcot 2xdx=a cos 8x+C, then
  1.    a=−116
  2.    a=18
  3.    a=116
  4.    a=−18
 Discuss Question
Answer: Option C. -> a=116
:
C
cos8x+1tan2xcot2xdx=2cos24xsin22xcos22x.sin2xcos2xdx=sin4xcos4xdx=12sin8xdx=116cos8x+Ca=116
Question 14. 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 15. x4+11+x6 dx=
  1.    tan−1(x)−tan−1(x3)+c
  2.    tan−1(x)−13tan−1(x3)+c
  3.    tan−1(x)+tan−1(x3)+c
  4.    tan−1(x)+13tan−1(x3)+c
 Discuss Question
Answer: Option D. -> tan−1(x)+13tan−1(x3)+c
:
D
I=x4+11+x6dx=(x4x2+1)+x2(1+x6)dx=x4x2+11+x6dx+x21+x6dx=11+x2dx+133x21+x6dx=tan1(x)+13tan1x3+c
Question 16. If Φ(x)=dxsin12x cos72x, then Φ(π4)Φ(0)=
  1.    125
  2.    95
  3.    65
  4.    0
 Discuss Question
Answer: Option A. -> 125
:
A
tanx=tsec2xdx=dtf(x)=dxsin12xcos12x.cos4x=(1+tan2x)sec2xtanxdx=(1+t2)tdt=(t1/2+t3/2)dt=2t1/2+25t5/2=2tanx+25(tanx)5/2ϕ(π4)ϕ(0)=2+25=125
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. x22x3x21dx is equal to
  1.    x2√x2−1
  2.    −x2√x2−1
  3.    √x2−1x2
  4.    −√x2−1x2
 Discuss Question
Answer: Option D. -> −√x2−1x2
:
D
x22x3x21dx=dxxx212dxx3x21=sec1x2secθtanθsec3θtanθdθ=[putx=secθdx=secθtanθdθ]=sec1x2cos2θdθ=sec1x2(1+cos2θ)dθ=sec1x(θ+sin2θ2)+C=sec1xsec1xx21x2+C=x21x2+C
Question 19. 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 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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