Theorem 13.1.11 (Convex Properties).label Let $c\suf\R^{n}$ be nonempty then
- (1)
$Conv(c)$ is the smallest convex set containing $c$
- (2)
$c$ is convex if and only if $Conv(c)=c$
- (3)
$Conv(c)=\curl{\sums{m}{i=1}\lam_ix_i:\curl{\lam_i}_1^m\suf[0,1],\curl{x_i}_1^m\suf c,\sums{m }{i=1}\lam_i=1}$
Proof.
- (1)
Follows from Lemma 13.1.4
- (2)
We note $c\suf c$ so if $c$ is convex then $Conv(c)\suf c$ hence $Conv(c)=c$. Conversely $Conv(c)$ is convex.
- (3)
Check
$\square$
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