Prove if C is midpoint convex and closed then its a convex set
16943
Midpoint-Convex and Continuous Implies Convex
121095
Is convex hull of a finite set of points in $\mathbb R^2$ closed?
10180
How to prove that this set is closed?
54600
Is a convex and lower semicontinuous function defined on a closed and convex subset of $\mathbb{R}^n$ continuous?
94231
Prove that a non-empty closed convex $S$ has an extreme point iff it does not contain any line
153670
Prove that if $a \mid b$ and $b \mid c$, then $a \mid c$.
123732
Proving that the maximum of two convex functions is also convex
5738
Cancellation of addition on convex sets
58988
Composition of convex function and affine function
116382
Showing convexity of a function with the restriction over an arbitrary line
60887
$d_A(x) = \inf_{a \in A} \|x-a\|$ is convex if and only if $A$ is convex
131118
How to prove the midpoint of a chord is also the midpoint of the line segment defined by the points of intersection of other two chords with it?
42494
The boundary is a closed set
92774
Prove that a linear subspace of $C([0,1])$ is closed
110876
Prove that $p\mid \binom{p}{k},\ 0< k< p$
113922
Proof that the intersection of any finite number of convex sets is a convex set
149820
How do you prove the set $G = \{(x, f(x)) \mid x \in \mathbb R\}$ is closed?