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12th Grade > Mathematics

LIMITS CONTINUITY AND DIFFERENTIABILITY MCQs

Total Questions : 45 | Page 1 of 5 pages
Question 1. limxπ2cotxcosx(π2x)3 is equal to 
 
  1.    1
  2.    π2
  3.    116 
  4.    0 
 Discuss Question
Answer: Option C. -> 116 
:
C
limxπ2cotxcosx(π2x)3
Let x=π2+t
If xπ2,t0
limt0sinttant8t3
=limt0(tt33!+t55!+)(t+t33+2t515+)8t3
=116
We can put x=π2t and we'll get L.H.L also same.
Since L.H.L = R.H.L the limit exists and is =116
Question 2. limx{x4sin(1x)+x21+|x|3} is equal to 
 
  1.    2 
  2.    1 
  3.    −1
  4.    does not exist
 Discuss Question
Answer: Option C. -> −1
:
C
limx[x4sin(1x)+x21+|x|3]
limxx31+|x|3[xsin(1x)+1x]
As x
x31+|x|3=1
xsin(1x)+1x=1
limxx31+|x|3(xsin1x+1x)=1
Question 3. If limx0((an)nxtanx)sinnxx2=0 where n is nonzero real number, then a is equal to
 
  1.    0
  2.    n+1n 
  3.    n 
  4.    n+1n 
 Discuss Question
Answer: Option D. -> n+1n 
:
D
limx0((an)nxtanx)sinnxx2=0
limx0((an)n(tanxx)).sinnxnx.n=0
((an)n1).1.n=0
a=1n+n
Question 4. The value of limx1(tanxπ4)tanπx2 is 
  1.    e−2
  2.    e−1
  3.    e
  4.    1 
 Discuss Question
Answer: Option B. -> e−1
:
B
limx1(tanxπ4)tanπx2(1from)
elimx1(tanxπ41)tanπx2
=elimx1(sinπx4cosπx4cosπx4)2sinπx4cosπx4cosπx2
=elimx12sin2πx42sinπx4cosπx4cosπx2
=elimx1(1cosπx2sinπx2cosπx2)
=elimx1(1sinπx2cosπx21)
=elimx1(cosπx21+sinπx21)
= e1
Question 5. f(x)={4x3,x<1x2x1, then
limx1f(x)=
  1.    1
  2.    −1
  3.    0
  4.    0
 Discuss Question
Answer: Option A. -> 1
:
A
limx1f(x)=limx1(4x3)=1
limx1+f(x)=limx1+x2=1
Since LHL = RHL
limx1f(x)=1
Question 6. The function f(x)=log(1+ax)log(1bx)x is not defined at x-0 . The value which should be assigned to f at x = 0 so that it is continuos at x=0 , is                                 
  1.    a-b
  2.    a+b
  3.    log a+log b
  4.    log a-log b
 Discuss Question
Answer: Option B. -> a+b
:
B
Since limit of a function is a + b as x 0, therefore to be continuous at a function, its value must be
a + b at x = 0 f(0) = a + b.
Question 7. limn 20x=1 cos 2n(x10) is equal to
  1.    0
  2.    1
  3.    19
  4.    20
 Discuss Question
Answer: Option B. -> 1
:
B
limncos2nx = {1,x=rπ,rI0,xrπ,rI
Here, for x = 10, limncos2n(x10) = 1
and in all other cases it is zero
limn20x=1cos2n(x10) = 1
Question 8. limnan+bnanbn, where a>b>1, is equal to 
  1.    −1
  2.    1
  3.    0
  4.    ab
 Discuss Question
Answer: Option B. -> 1
:
B
limnan+bnanbn
a>b>1
=nn1+(ba)n1(ba)n
=1
Question 9. If f(x) = {sinxxnπ,n=0,±1,±2...2,otherwise and g(x) = x2+1,x0,24,x=05,x=2, then limx0g{f(x)} is 
  1.    2
  2.    0
  3.    3
  4.    1
 Discuss Question
Answer: Option D. -> 1
:
D
Given that,
f(x) = {sinxxnπ,n=0,±1,±2...2,otherwise
and
g(x) = x2+1,x0,24,x=05,x=2
Then limx0g[f(x)]=limx9g(sinx)
=limx0(sin2x+1)=1
Question 10. limx0sinxx+x36x5 is equal to
  1.    1120
  2.    1160
  3.    12
  4.    0
 Discuss Question
Answer: Option A. -> 1120
:
A
limx0sinxx+x36x5 ....... (1)
We know expansion of Sinx.
sinx=xx33!+x55!+ ........ (2)
Substituting (2) in (1) we get
limx0x55!.x5
=15!
=1120

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