JEE AdvancedHardQuestion 240017
Question
If f(x) = x² sin(1/x) for x ≠ 0 and f(0) = 0, then f is:
- AContinuous at 0 but not differentiable
- BBoth continuous and differentiable at 0Correct
- CNeither continuous nor differentiable
- DDifferentiable but not continuous
Correct answer
Both continuous and differentiable at 0
Explanation
Continuity: |f(x)| = |x² sin(1/x)| ≤ x² → 0 as x → 0 = f(0) ✓. Differentiability: f'(0) = lim(x→0) f(x)/x = lim x sin(1/x). Since |x sin(1/x)| ≤ |x| → 0, f'(0) = 0 ✓.