whats-the-mean-R-and-R-

Question Number 71551 by mhmd last updated on 17/Oct/19

w h a t s t h e m e a n R^{+ +} ? a n d R^{- -} ?

Answered by MJS last updated on 17/Oct/19

I only know R^{+} = {x \in R ∣ x > 0} and

R^{-} = {x \in R ∣ x < 0}

and

R \times R = R^{2} = {(\begin{matrix} x \\ y \end{matrix}) ∣ x \in R \land y \in R}

so maybe

R^{+ +} = R^{+} \times R^{+} = {(\begin{matrix} x \\ y \end{matrix}) \in R^{2} ∣ x > 0 \land y > 0}

and similar for R^{- +}, R^{- -}, R^{+ -}

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