Constructivisme
Made in
I wanted to represent “constructions” with a formula.
The displayed formula illustrates a mathematic formula with a simple proof that is not constructive. Precisely, the formula says that it exists two irrationals 
and 
such that to the power of is rational.
Proof: if $\sqrt{2}^\sqrt{2}$ is rational, just set both and to be equal to $\sqrt{2}$. Otherwise, set to be $\sqrt{2}^\sqrt{2}$ and to be $\sqrt{2}$, we then obtain that to the power of is equal to 2, so it is rational.
In the end, we proved the formula, but we do not know which and works.
