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JG89
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If a function f is differentiable at a point x = c of its domain, then must it also be differentiable in some neighborhood of x = c?
continuous at x=0? Isn't it necessary for a function to be continuous at a point c for it to be derivable at c?[tex]
f(x) = \left\{\begin{array}{lr}x^2&x\in\mathbb{Q}\\-x^2&x\not\in\mathbb{Q}\end{array}
[/tex]
BobbyBear said:And what does it mean to be continuous at a point?
I don't think so. Take any continuous function f differentiable at c and any continuous, nowhere differentiable function g bounded in some neighbourhood of 0 (such as the Weierstrass function). Then f(x) + (x-c)*g(x-c) should be continuous, differentiable at c, but not differentiable on any neighbourhood of c.Cantab Morgan said:Good catch, slider142! Okay, for fun let's emend the question a bit...
Given an function that is continuous in some neighborhood of c and differentiable at c, must it also be differentiable in some neighborhood of c?
Continuity at a point only means that nearby points approach a, not that it's continuous near a.
When a function is differentiable at a point, it means that the derivative of the function exists at that point. In other words, the function has a well-defined slope at that particular point.
To determine if a function is differentiable at a specific point, you can use the limit definition of the derivative. If the limit exists and is finite, then the function is differentiable at that point.
A function being differentiable at a point tells us that the function is smooth and has no abrupt changes at that point. It also allows us to calculate the slope of the function at that point, which is useful in many applications.
Yes, a function can be differentiable at some points but not others. This typically occurs when a function has a sharp corner or a vertical tangent at a certain point, making the derivative undefined at that point.
A function must be continuous at a point in order to be differentiable at that point. However, a function can be continuous at a point but not differentiable, as it may have a sharp corner or a vertical tangent at that point.