# GCD = 1

**Number Theory**Level 2

For a positive integer \(n>2,\) what can we say about the number of positive integers less than \(n\) that are relatively prime to \(n\) (that is, their GCD is 1)?

Hint: A useful property of the Greatest Common Divisor function is \(\gcd(a,b) = \gcd(a,a-b);\) e.g., \(\gcd(10,8) = \gcd(10,2) = 2.\)