For what values of $b\in \mathbb R$ is $\pi-b$ rational? Just a simple short question.
I'm looking for values $b$ such that $\pi-b$ is a rational number. 
Obviously $\pi$ is such a number, but are there more?
Edit: $b$ is in $\mathbb R$

Clearly, and almost vacuously $b=\pi+q$ for some rational number $q$. You can easily show that these are the only ones.
