A
rational number can be defined as the quotient of two
integers (as long as the denominator is non-zero). A more detailed definition goes as follows: : A real number
r is rational, if and only if it can be expressed as a quotient of two integers with a nonzero denominator. A real number that is not rational is irrational. Or more formally: : Given a real number
r,
r is rational if and only if there exists integers
a and
b such that r = \tfrac a b and b \neq 0. The existence of
irrational numbers—numbers that are not a quotient of two integers—was first discovered in geometry, in such things as the ratio of the diagonal to the side in a square. == More general quotients ==