What is the range of the function ?

MATHEMATICS · Single correct · AoPS · Mathematics · Special Functions · Special Functions

Problem

What is the range of the function f(x)=sgn⁡(x)f(x)=\operatorname{sgn}(x)? (a) {−1,1}\{-1,1\} (b) R\mathbb{R} (c) {−1,0,1}\{-1,0,1\} (d) [0,∞)[0,\infty)

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