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What is the coX of {(x,y) $\in$ $\mathbb R^2$ : y = $1\over1+x$, $x \ge 0$ } ?

coX is the convex hull.

I couldn't figure out. coX should be the smallest convex set that contains the set but in this case should it be the hyperbola itself. Thanks for helping.

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    Technically that's a *hyperbola* in English. "Hyperbole" is a non-scienti$f$ic word that means "exaggeration".2012-11-01

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I think $co(X) = \{ (x,y) \in \mathbb{R}^2 : x > 0, \frac{1}{1+x} \leq y < 1 \} \cup {(0,1)}$. The basic idea is, you want to start from the point $(0,1)$ and draw a ray to anywhere on $X$, and the entire ray must be included in the $co(X)$.

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    @teodory agree.2012-11-01