The function fx sexx is not defined for the following real n

The function f(x)= sex(x) is not defined for the following real numbers, where k is an integer.

Solution

Secx is inverse of cosx. So it will not be defined where value of cosx will go to zero. at /2 value of cosx is zero so cosx will not define at this value. So option A is true.

i.e. x = k + /2