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In complex analysis, complex-differentiability is defined using the same definition as single-variable real functions. This is allowed by the possibility of dividing complex numbers . So, a function f : C → C {\textstyle f:\mathbb {C} \to \mathbb {C} } is said to be differentiable at x = a {\textstyle x=a} when
Continuity and differentiability This function does not have a derivative at the marked point, as the function is not continuous there (specifically, it has a jump discontinuity ). 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 ...
A continuity equation or transport equation is an equation that describes the transport of some quantity. It is particularly simple and powerful when applied to a conserved quantity , but it can be generalized to apply to any extensive quantity .
The concept of continuity for functions between metric spaces can be strengthened in various ways by limiting the way depends on and c in the definition above. Intuitively, a function f as above is uniformly continuous if the δ {\displaystyle \delta } does not depend on the point c .
Differentiability is therefore a stronger regularity condition (condition describing the "smoothness" of a function) than continuity, and it is possible for a function to be continuous on the entire real line but not differentiable anywhere (see Weierstrass's nowhere differentiable continuous function). It is possible to discuss the existence ...
Only continuity of , not differentiability, is needed at the endpoints of the interval . No hypothesis of continuity needs to be stated if I {\displaystyle I} is an open interval , since the existence of a derivative at a point implies the continuity at this point.
In calculus and real analysis, absolute continuity is a smoothness property of functions that is stronger than continuity and uniform continuity. The notion of absolute continuity allows one to obtain generalizations of the relationship between the two central operations of calculus — differentiation and integration .
Its derivative is essentially bounded in magnitude by the Lipschitz constant, and for a < b, the difference g(b) − g(a) is equal to the integral of the derivative g′ on the interval [a, b]. Conversely, if f : I → R is absolutely continuous and thus differentiable almost everywhere, and satisfies | f′ ( x )| ≤ K for almost all x in I ...