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For a function to have an inverse, it must be one-to-one.If a function is not one-to-one, it may be possible to define a partial inverse of by restricting the domain. For example, the function = defined on the whole of is not one-to-one since = for any .
Similarly, every additive function that is not linear (that is, not of the form for some constant ) is a nowhere continuous function whose restriction to is continuous (such functions are the non-trivial solutions to Cauchy's functional equation). This raises the question: can such a dense subset always be found?
For example, the cosine function is injective when restricted to the interval [0, π]. The image of this restriction is the interval [−1, 1], and thus the restriction has an inverse function from [−1, 1] to [0, π], which is called arccosine and is denoted arccos. Function restriction may also be used for "gluing" functions together.
A function defined on a rectangle (top figure, in red), and its trace (bottom figure, in red). In mathematics, the trace operator extends the notion of the restriction of a function to the boundary of its domain to "generalized" functions in a Sobolev space.
Download as PDF; Printable version; ... For example, if g(x) ... For example, an analytic function is the limit of its Taylor series, ...
For example, the map : [,) defined by the polynomial () = is a continuous open surjection with discrete fibers so this result guarantees that the maximal open subset is dense in ; with additional effort (using the inverse function theorem for instance), it can be shown that = {}, which confirms that this set is indeed dense in .
In mathematics, a surjective function (also known as surjection, or onto function / ˈ ɒ n. t uː /) is a function f such that, for every element y of the function's codomain, there exists at least one element x in the function's domain such that f(x) = y. In other words, for a function f : X → Y, the codomain Y is the image of the function ...
In mathematics, a corestriction [1] of a function is a notion analogous to the notion of a restriction of a function. The duality prefix co- here denotes that while the restriction changes the domain to a subset, the corestriction changes the codomain to a subset. However, the notions are not categorically dual.