What is the domain of f(x) = cos(x)? the set of real numbers Negative 2 pi less-than-or-equal-to x less-than-or-equal-to 2 pi the set of real numbers Negative 1 less-than-or-equal-to x less-than-or-equal-to 1 the set of real numbers 0 less-than-or-equal-to x less-than-or-equal-to 2 pi the set of all real numbers