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📐 Mathematics  ·  Continuity and Differentiability  ·  JEE

If f(x) = x sin(1/x) for x not 0 and f(0) = 0, is f continuous at x = 0?

Answer: Yes, since x sin(1/x) is squeezed between -|x| and |x| which go to 0.

  • A No, the limit does not exist since sin(1/x) oscillates without settling
  • B Yes, since x sin(1/x) is squeezed between -|x| and |x| which go to 0
  • C No, because sin(1/x) oscillates infinitely often near x = 0
  • D Cannot be determined without evaluating the one-sided limits separately

Correct answer: B. Yes, since x sin(1/x) is squeezed between -|x| and |x| which go to 0

Explanation: Since |x sin(1/x)| <= |x|, by the squeeze theorem the limit as x approaches 0 is 0, which equals f(0), so f is continuous at 0.

f(x) = |x|: Continuous but NOT Differentiable at 0x=0 (sharp "kink")LHD = -1RHD = +1LHD ≠ RHD at the kink → not differentiable, even though the curve has no gap (continuous)

f(x)=|x| is perfectly continuous at x=0 (no break, no jump), but the curve has a sharp corner there: approaching from the left gives slope -1 and from the right gives slope +1 - since these one-sided derivatives disagree, the function is not differentiable at that point.

Concept context

When a function has no breaks (continuity) and when it has a well-defined slope (differentiability), plus rules for differentiating implicit, inverse trig, exponential, log, and parametric functions.

Read the full Continuity and Differentiability notes →