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12th Grade > Mathematics

LIMITS CONTINUITY AND DIFFERENTIABILITY MCQs

Total Questions : 45 | Page 3 of 5 pages
Question 21. limαβsin2αsin2βα2β2 is equal to 
  1.    sin3β(4β) 
  2.    sin2β(2β)
  3.    sin8β(7β)
  4.    sin6β(4β)
 Discuss Question
Answer: Option B. -> sin2β(2β)
:
B
limαβsin2αsin2βα2β2=limαβsin(αβ)sin(α+β)(αβ)(α+β)=sin2β(2β)
Question 22. limxx+sinxxcosx=
  1.    0
  2.    1
  3.    −1
  4.    does not exist
 Discuss Question
Answer: Option B. -> 1
:
B
limxx+sinxxcosx
=limxx121+sinxxx121cosxx
We know, that for any value of x, sinx and cosx will be [-1,1]
So,=limxSinxx=0
And =limxCosxx=0
=x121+sinxx1+sinxx1+cosxx
=limx11
=1
Question 23. If f(x)={x23,2<x<32x+5,3<x<4, the equation whose roots are limx3f(x) and limx3+f(x) is
  1.    x2−12x+36=0
  2.    x2−26x+66=0
  3.    x2−17x+66=0
  4.    x2−22x+121=0
 Discuss Question
Answer: Option C. -> x2−17x+66=0
:
C
f(x)={x23,2<x<32x+5,3<x<4
limx3f(x)=limx3(x23)=6
and limx3+f(x)=limx3+(2x+5)=11
Hence, the required equation will be
x2 - (sum of roots)x + (Products of roots) = 0
Question 24. The value of limxπ2[sin1sinx],[x] is the greatest integer function of x, is
  1.    1
  2.    π2
  3.    0
  4.    12
 Discuss Question
Answer: Option A. -> 1
:
A
limxπ2[sin1sinx]
= limxπ2[x]
= 1
Question 25. limx(2+x)40(4+x)5(2x)45
  1.    −1
  2.    1
  3.    16
  4.    32
 Discuss Question
Answer: Option A. -> −1
:
A
limx(2+x)40(4+x)5(2x)45
=limxx45(2x+1)40(4x+1)5x45(2x1)45
=(1)40(1)5(1)45
=(1)45(1)45
=1
Question 26. limnnr=1cot1(r2+34) is
  1.    0
  2.    tan−11
  3.    tan−12
  4.    tan−112
 Discuss Question
Answer: Option C. -> tan−12
:
C
limnnr=1tan1(44r2+3)
=limnnr=1tan1(1r214+1)
=limnnr=1tan1((r+12)(r12)1+(r+12)(r12))
=limnnr=1tan1{tan1(r+12)tan1(r12)}
=limn{tan1(n+12)tan1(12)}
= π2tan112
= tan12
Question 27. If G(x) = - 25x2 then limx1G(x)G(1)x1 has the value 
 
  1.    124
  2.    15
  3.    −√24
  4.    12√6
 Discuss Question
Answer: Option D. -> 12√6
:
D
limx125x2(24)x1
=limx12425x2x1×24+25x224+25x2
limx1x21(x1)[24+25x2]=2224=126
Question 28. limx2x2+x2x24 is equal to 
  1.    12 
  2.    1 
  3.    2 
  4.    0 
 Discuss Question
Answer: Option A. -> 12 
:
A
limx2x2+x2x24
=limx2(x2x+2x2+x2x24)
On rationalisation -
=limx2(1x+2+x2x24(x+2))
=limx21x+2+limx2x2x+2×1x+2
=12
Question 29. limn2.3n3.5n3.3n+4.5n=
  1.    23 
  2.    −34
  3.    1 
  4.    0 
 Discuss Question
Answer: Option B. -> −34
:
B
limn2.3n3.5n3.3n+4.5n
=limn5n(2(35)n3)5n(3(35)n+4)
Asn,(35)n0
=34
Question 30. limx0(1+2x1+3x)1x2.e1x=
  1.    e52
  2.    e2
  3.    2
  4.    1
 Discuss Question
Answer: Option A. -> e52
:
A
limx0e1x2(log(1+2x)log(1+3x))+1xelimx0(log(1+2x)log(1+3x))+xx2
Using the expansion we get -
=e52

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