Definition:Rational Convex

Definition
Let $f: I \to \R$ be a real function defined on a real interval $I$.

Then $f$ is called rational convex on $I$ :


 * $\forall x,y \in I: \forall t\in \closedint 0 1 \cap \Q: \map f {t x + \paren{1-t} y} \le t \map f x + \paren{1-t} \map f y$