Which function has a domain of all real numbers A y secx B

Which function has a domain of all real numbers? A. y = secx B. y = cosx C. y = tanx D. y = 1/sin x

Solution

Functions sec(x) and tan(x) are not defined when x = (2n+1)/2 (where n is an integer)

Similarly, function 1/sin(x) is not defined when x = n (where n is an integer)

Cos(x) is defined for all the real values of x

Hence, the only option that has domain of all real numbers is function y = cos(x).

Option B