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It is differentiable everywhere except at the point x = 0, where it makes a sharp turn as it crosses the y-axis. A cusp on the graph of a continuous function. At zero, the function is continuous but not differentiable. If f is differentiable at a point x 0, then f must also be continuous at x 0. In particular, any differentiable function must ...
is everywhere continuous. However, it is not differentiable at = (but is so everywhere else). Weierstrass's function is also everywhere continuous but nowhere differentiable. The derivative f′(x) of a differentiable function f(x) need not be continuous. If f′(x) is continuous, f(x) is said to be continuously differentiable.
If a continuous function on an open interval (,) satisfies the equality () =for all compactly supported smooth functions on (,), then is identically zero. [1] [2]Here "smooth" may be interpreted as "infinitely differentiable", [1] but often is interpreted as "twice continuously differentiable" or "continuously differentiable" or even just "continuous", [2] since these weaker statements may be ...
This function is continuous on the closed interval [−r, r] and differentiable in the open interval (−r, r), but not differentiable at the endpoints −r and r. Since f (−r) = f (r), Rolle's theorem applies, and indeed, there is a point where the derivative of f is zero. The theorem applies even when the function cannot be differentiated ...
A version of the fundamental theorem of calculus holds for the Gateaux derivative of , provided is assumed to be sufficiently continuously differentiable. Specifically: Specifically: Suppose that F : X → Y {\displaystyle F:X\to Y} is C 1 {\displaystyle C^{1}} in the sense that the Gateaux derivative is a continuous function d F : U × X → Y ...
The absolute value function is continuous but fails to be differentiable at x = 0 since the tangent slopes do not approach the same value from the left as they do from the right. If f {\displaystyle f} is differentiable at a {\displaystyle a} , then f {\displaystyle f} must also be continuous at a {\displaystyle a} . [ 11 ]
More precisely, if all the partial derivatives of at exist and are continuous in a neighborhood of , then is differentiable at . When this happens, then in addition, the total derivative of f {\displaystyle f} is the linear transformation corresponding to the Jacobian matrix of partial derivatives at that point.
A function is called locally Lipschitz continuous if for every x in X there exists a neighborhood U of x such that f restricted to U is Lipschitz continuous. Equivalently, if X is a locally compact metric space, then f is locally Lipschitz if and only if it is Lipschitz continuous on every compact subset of X. In spaces that are not locally ...