You've been doing that all this time and didn't even realize it !
Every plain old number that you ever see is a rational number.
Every equation that has plain old numbers next to the variables
is an equation with rational coefficients.
If a variable ever has (pi) or a square root or a trig function next to it,
then that's an irrational coefficient. But I'll just bet you haven't ever
seen any of these yet.
