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12th Grade > Mathematics

DEFINITE INTEGRATION MCQs

Total Questions : 30 | Page 2 of 3 pages
Question 11. π2π2 sin2x dx=
  1.    π
  2.    π2
  3.    π2−12
  4.    π−1
 Discuss Question
Answer: Option B. -> π2
:
B
π2π2sin2xdx=2π20sin2xdx=2r(32)r(12)2r(2+22)=π2
Question 12. Find the integral 0exdx.
  1.    0
  2.    1
  3.    2
  4.    ∞
 Discuss Question
Answer: Option B. -> 1
:
B
We can see that the given integral is an improper integral as one of its limits is not finite.
In such cases where we have to deal with infinity as the limits of definite integral, we’ll change the limit which is not finite to a variable and then put the limits.
0exdx=limaa0exdx
=lima(ex)a0
=lima(ea(e0))
=0(1)
=1
Question 13. π20 log(tan x+cot x)dx=
  1.    π log 2
  2.    −π log 2
  3.    −π2 log 2
  4.    π2 log 2
 Discuss Question
Answer: Option A. -> π log 2
:
A
π20log(tanx+cotx)dx=π20log[2sin2x]dx
=π20(log2logsin2x)dx=log2(π2)+(π2)log2=πlog2
Question 14. 10π0|sin x|dx is
  1.    20
  2.    8
  3.    10
  4.    18
 Discuss Question
Answer: Option A. -> 20
:
A
10π0|sinx|dx=10π0|sinx|dx
|sinx|is positive in I & II quadrant and has period π
=10π0sinxdx=10[cosx]x0=20
Question 15. Calculate 32f(x)dx where
f(x)={6ifx>13x2ifx1
 
  1.    19
  2.    21
  3.    17
  4.    15
 Discuss Question
Answer: Option B. -> 21
:
B
Calculate ∫3−2f(x)dx Wheref(x)=6ifx>13x2ifx≤1 
Here, we can see that the integrand f(x) in not continuous in the interval (-2, 3) as it has a discontinuity at x = 1. So we can’t just integrate f(x) and put limits.We’ll have to break this integral into integrals which have limits such that integrands is continuous in those limits.
32f(x)dx=123x2dx+316dx
Now we can integrate these integrands and put limits.
123x2dx+316dx=(x3)|12+(6x)|31=1(8)+186
= 21
Question 16. limπ199+299+399+n99n100= [EAMCET 1994]
  1.    9100
  2.    1100
  3.    199
  4.    1101
 Discuss Question
Answer: Option B. -> 1100
:
B
limπ199+299+399+n99n100=limπnr=1(r99n100)
=limπ1nnr=1(rn)99=10x99dx=[x100100]10=1100
Question 17. The value of the definite integral 10x dxx3+16 lies in the interval [a, b]. The smallest such interval is.
  1.    [0,117]
  2.    [0,1]
  3.    [0,127]
  4.    None of these
 Discuss Question
Answer: Option A. -> [0,117]
:
A
f(x)=xx3+16f(x)=162x3(x3+16)2f(x)=0x=2Alsof′′(2)<0 The function f(x)=xx3+16 is an increasing function in [0,1], so Min f(x) = f(0) = 0 and Max f(x) = f(1) = 117
Therefore by the property m(ba)baf(x)dxM(ba)
(where m and M are the smallest and greatest values of function)
010xx3+16dx117
Question 18. π20 cos x1+sin xdx=
  1.    log 2
  2.    log e
  3.    12 log 3
  4.    0
 Discuss Question
Answer: Option A. -> log 2
:
A
put 1+ sin x =t
Thenπ20cosx1+sinxdx=[log|1+sinx|]π20=log2
Question 19. If x0f(t)dt=x+1xt f(t) dt, then the value of f(1) is      [IIT 1998; AMU 2005]
 
  1.    12
  2.    0
  3.    1
  4.    −12
 Discuss Question
Answer: Option A. -> 12
:
A
x0dt=x+1xtf(t)dt1xtf(t)dt=xx1tf(t)dt
Differentiating w.r.t x, we get f(x)=1+{0xf(x)}
f(x)=1xf(x)(1+x)f(x)=1f(x)=11+x
f(1)=11+1=12
Question 20. In=10xntan1xdx. If anIn+2+bnIn=cn  nϵN,n1 then
  1.    a1,a2,a3.....are in A.P.
  2.    b1,b2,b3.....are in G.P.
  3.    c1,c2,c3.....are in H.P.
  4.    a1,a2,a3.....are in H.P.
 Discuss Question
Answer: Option A. -> a1,a2,a3.....are in A.P.
:
A
In=(xn+1n+1tan1x)1010xn+1n+1.11+x2dx(n+1)In=π410xn+11+x2dx(n+3)In+2=π410xn+31+x2dx(n+1)In+(n+3)In+2=π21n+2an=(n+3)a1,a2,a3.....are in A.P.
bn=(n+1)b1,b2..... are in A.P.
cn=π21n+2 not in any progression.

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