# Answer to Question #16021 in Real Analysis for Ciaran Duffy

Question #16021

Let f(x) = |x|^1/2. Is f differentiable at c = 0?

Expert's answer

Notice that for x>0,

f'(x) = 1/2 * x^(1/2-1) = 1/2 * x^(-1/2) = 1/( 2

x^(1/2) ).

Hence when x->0

lim_{x->0} f'(x) = +

infinity.

Therefore f is not differentiable at c=0 since f' in unbounded

at that point.

f'(x) = 1/2 * x^(1/2-1) = 1/2 * x^(-1/2) = 1/( 2

x^(1/2) ).

Hence when x->0

lim_{x->0} f'(x) = +

infinity.

Therefore f is not differentiable at c=0 since f' in unbounded

at that point.

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