Q27 / 93 · NTA Abhyas (JEE Main) 2020 · Mathematics · Continuity and Differentiability

If f:R→R is a function defined by f(x)=xsin2x-12π, where x denotes the greatest integer function, then f is

  • A
    continuous for every real x
  • B
    discontinuous only at x=0
  • Correct answer
    C
    discontinuous only at integral values of x
  • D
    continuous only at x=0

Solution

Doubtful points are x=n, ∀n∈Ι
L.H.L=limx→n-xsin2x-12π
=n-1sin2n-12π=±n-1
R.H.L=limx→n+xsin2x-12π
=nsin2n-12π=±n
fn=±n 
Clearly, LHL,RHL, fn all cannot be equal for any n∈Ι
Hence, discontinuous at all integeral values of x

Hence, the correct answer is option: 'C'.

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