Can you tell me what does it mean by that? http://screencast.com/t/kqhQ7zAQp

Question

amistre64 · Answer

there are 2 types of critical points:  f' = 0, and f' = undefined.

amistre64 · Answer

a stationary point, are the places along the curve that have a rate of change of zero ... they aint moving

anonymous · Answer

yeah.. and another type of stationary points, in addition to critical points, are those where the function isn't differentiable...

christos · Answer

what do you mean is not differentiable? How can it be?

amistre64 · Answer

take y = x^{1/3}

y' = 1/x^{2/3}

this is undefined, nondifferentiable at x=0

anonymous · Answer

not differentiable is the point where the derivative doesn't exist.. 

example: a function isn't differentiable if f '(a) doesn't exist for that value of x=a.

amistre64 · Answer

even tho the x^{1/3} (cuberoot of x) is continuous at x=0, it has no definable value for a derivative at x=0

anonymous · Answer

@amistre64's reply hits the nail on its head..

christos · Answer

thank you