What I learnt in class today:

A convex function f:\mathbb R\to\mathbb R is defined as satisfying

f(\lambda x + (1-\lambda )y)\leq \lambda f(x)+(1-\lambda )f(y) \quad \forall x,y\in \mathbb R,\ \forall \lambda \in [0, 1].

 

Thus, the shape of a convex function is like \smallsmile . An example of a convex function is f(μ)=μ2:

 

How clear is this post?