Does anyone know how to tell the difference between rational and irrational numbers?

Rational numbers refers to a number that can be expressed in a ratio of two integers. An irrational number is one which can't be written as a ratio of two integers. Expressed in fraction, where denominator ≠ 0. Cannot be expressed in fraction.

Step-by-step explanation:

done

check the picture below.

well, the angle at the vertex d is clearly not a right-angle, let's check for the one at the vertex f which does look like,   however if it's indeed, that means ef is perpendicular to df, in which case their slopes will be negative reciprocal of each other.

so the negative reciprocal of the slope of ef is 1, however the slope of df is not 1, is 1/2, so nope, they're not perpendicular lines.