- #1
hth
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Homework Statement
Determine that, if f(x) =
{xsin(1/x) if x =/= 0
{0 if x = 0
that f'(0) exists and f'(x) is continuous on the reals. (Sorry I can't type the function better, it's piecewise)
Homework Equations
The Attempt at a Solution
For f'(0) existing,
For x ≠ 0,
(f(x) - f(0))/(x - 0) = (x sin(1/x))/x = sin(1/x).
Sin(1/x) doesn't have a limit as x → 0 because the function oscillates between -1 and 1, f is not differentiable at x = 0. Therefore f'(0) doesn't exist.
For f'(x) being continuous.
For any given ɛ > 0, there exists δ > 0 such that |x - y| < δ and |f(x) - f(y)| < ɛ for all x, y on the reals.
For all x [tex]\in[/tex] R (R is the reals), ... and this where I'm stuck.