Limit Continuity and Differentiability 4 Question 3

3. Let [.] denotes the greatest integer function and f(x)=[tan2x], then

(1993, 1M)

(a) limx0f(x) does not exist

(b) f(x) is continuous at x=0

(c) f(x) is not differentiable at x=0

(d) f(0)=1

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Answer:

Correct Answer: 3. (b)

Solution:

  1. Given function

f(x)=a|πx|+1,x5b|xπ|+3,x>5

and it is also given that f(x) is continuous at

Clearly,

f(5)=a(5π)+1

limx5f(x)=limh0[a|π(5h)|+1]=a(5π)+1

and limx5+f(x)=limh0[b|(5+h)π|+3]

=b(5π)+3

Function f(x) is continuous at x=5.

f(5)=limx5+f(x)=limx5f(x)a(5π)+1=b(5π)+3(ab)(5π)=2ab=25π



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