$\displaystyle\pi\usepackage{cmbright}\Huge\$ is a non-terminating, non-repeating decimal, so it is an irrational number. Approximations of $\displaystyle\pi\usepackage{cmbright}\Huge\$ include the rational numbers 3.14159 and $\displaystyle\frac{{22}}{{7}}\usepackage{cmbright}\Huge\$ , but $\displaystyle\pi\usepackage{cmbright}\Huge\$ itself is irrational.