It's actually impossible to prove irrationality using only the data provided by the calculator since it can't represent irrational numbers with the OS supported data types. You're going to have to solve the problems yourself. Luckily, it's very easy.

Irrational numbers are those numbers that can't be represented as a/b, where a and b are integers. Rational numbers are everything else. Every square root of a number that is not a perfect square is irrational, along with pi and e. Integers are those numbers that have 0's after the decimal point. Negative integers are integers that have a negative sign (I seriously hope you can identify a negative sign). Everything that isn't irrational or an integer can be considered Rational, which for your purposes means it has a decimal component.