Question

Use a calculator to find the approximate value of arcsin(0.72).

Answer 1

Since the question specifically asks about using a calculator, there's no point explaining how to do it (mostly because the buttons you have to press vary from model to model.

All we can tell you is that the calculator, depending on how many decimal digits it can store, will return something like 0.803802...

Even if there were millions of digits after the decimal point, that would still be an approximate value, since this number is irrational, i.e. it has infinite, non-repeating decimal digits.