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Pointwise Operations on Real-Valued Maps

Defines the pointwise sum, product, scalar multiple, negative and difference of real-valued maps on a set, and the constant maps.

Statement

In the setting of Metric Spaces: Balls, the Metric Topology, and the Real and Complex Numbers as Metric Spaces, let II be a set, and let RI\mathbb{R}^{I} be the set of maps from II to R\mathbb{R}.

For f,g∈RIf,g\in\mathbb{R}^{I} and t∈Rt\in\mathbb{R}, the sum f+gf+g, the product fgfg, the scalar multiple tftf and the negative −f-f are the elements of RI\mathbb{R}^{I} with

(f+g)(p)=f(p)+g(p),(fg)(p)=f(p) g(p),(tf)(p)=t f(p),(−f)(p)=−f(p)(p∈I),(f+g)(p)=f(p)+g(p),\qquad (fg)(p)=f(p)\,g(p),\qquad (tf)(p)=t\,f(p),\qquad (-f)(p)=-f(p)\qquad(p\in I),

namely the values at (f,g)(f,g), (f,g)(f,g), (t,f)(t,f) and ff of the operations and maps of Pointwise Operations on Real-Valued Maps Exist and Are Unique §binary, Pointwise Operations on Real-Valued Maps Exist and Are Unique §scalar-multiple and Pointwise Operations on Real-Valued Maps Exist and Are Unique §negative. The product is written by juxtaposition only, never with a dot. The difference is f−g=f+(−g)f-g=f+(-g).

For c∈Rc\in\mathbb{R}, the constant map with value cc is the h∈RIh\in\mathbb{R}^{I} with h(p)=ch(p)=c for all p∈Ip\in I, given by Pointwise Operations on Real-Valued Maps Exist and Are Unique §constant. Where an element of RI\mathbb{R}^{I} is required, 00 and 11 denote the constant maps with values 00 and 11.

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