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12th Grade > Mathematics

INTEGRALS MCQs

Total Questions : 30 | Page 3 of 3 pages
Question 21. The value of ax2bxc2x2(ax2+b)2dx is equal to
  1.    sin−1[ax+bxc]+k
  2.    sin−1[ax2+bx2c]+k
  3.    cos−1[ax+bxc]+k
  4.    cos−1[ax2+bx2c]+k
 Discuss Question
Answer: Option A. -> sin−1[ax+bxc]+k
:
A
I=abx2c2(ax2+bx)2dx=(abx2)c2(ax+bx)2dx
Put ax+bx=t(abx2)dx=dtI=dtc2t2=sin1[ax+bxc]+k
Question 22. 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 23. Let x2nπ1,nϵN. Then, the value of x2sin(x2+1)sin2(x2+1)2sin(x2+1)+sin2(x2+1)dx is equal to
  1.    log|12sec(x2+1)|+C
  2.    log|sec(x2+12)|+C
  3.    12log|sec(x2+1)|+C
  4.    None of these
 Discuss Question
Answer: Option B. -> log|sec(x2+12)|+C
:
B
We have, x2sin(x2+1)sin2(x2+1)2sin(x2+1)+sin2(x2+1)dx=x2sin(x2+1)2sin(x2+1)cos(x2+1)2sin(x2+1)+2sin(x2+1)cos(x2+1)dx=x1cos(x2+1)1+cos(x2+1)dx=xtan(x2+12)dx=tan(x2+12)d(x2+12)=log|sec(x2+12)|+C
Question 24. dxcos(2x)cos(4x)is equal to
  1.    12√2log|1+√2 sin 2x1−√2 sin 2x|−12(log|sec 2x+tan 2x|)+C
  2.    12√2log|1+√2 sin 2x1+√2 sin 2x|−12(log|sec 2x+tan 2x|)+C
  3.    1√2log|1+√2 sin 2x1+√2 sin 2x|−12(log|sec 2x−tan 2x|)+C
  4.    None of these
 Discuss Question
Answer: Option A. -> 12√2log|1+√2 sin 2x1−√2 sin 2x|−12(log|sec 2x+tan 2x|)+C
:
A
sin(4x2x)dxsin(2x)cos(2x)cos(4x)=sin(4x)dxsin(2x)cos(4x)sec2xdx=2cos2xdxcos4x12(log|sec2x+tan2x|)
Question 25. ex[x3+x+1(1+x2)3/2]dx is equal to
  1.    x2ex(1+x2)1/2+c
  2.    exx(1+x2)1/2+c
  3.    ex(1+x2)1/2+c
  4.    xex(1+x2)1/2+c
 Discuss Question
Answer: Option D. -> xex(1+x2)1/2+c
:
D
I=ex[x1+x2+1(1+x2)3/2]dx
Let f(x)=x1+x2f(x)=1+x2x21+x2(1+x2)
=1(1+x2)3/2
I=exf(x)+c
=exx1+x2+c
Question 26. dxsin4x+cos4x is equal to
  1.    1√2tan−1(1√2tan 2x)+C
  2.    √2tan−1(1√2tan 2x)+C
  3.    1√2tan−1(1√2cot 2x)+C
  4.    None of these
 Discuss Question
Answer: Option A. -> 1√2tan−1(1√2tan 2x)+C
:
A
dxsin4x+cos4x=dx(sin2x+cos2x)22sin2xcos2x=2dx2sin22x=2sec22x2sec22xtan22xdx=2sec22x2+tan22xdx=dt(2)2+t2[puttingtan2x=t2sec22xdx=dt]=12tan1(t2)+C=12tan1(12tan2x)+C
Question 27. 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 28. 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 29. 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 30. cos3x+cos5xsin2x+sin4xdx equals
  1.    sinx−6tan−1(sinx)+c
  2.    sinx−2sin−1x+c
  3.    sinx−2(sinx)−1−6tan−1(sinx)+c
  4.    sinx−2(sinx)−1+5tan−1(sinx)+c
 Discuss Question
Answer: Option C. -> sinx−2(sinx)−1−6tan−1(sinx)+c
:
C
sinx=t;I=(1t2)(2t2)t2(1+t2)dt=(1+2t261+t2)dt
=sinx2(sinx)16tan1(sinx)+c

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