Question

Domain of f(x) = log(cosx)

a)" "[ 2npi - pi/2 , 2npi + pi/2 ]

b)" "( 2npi - pi/2 , 2npi + pi/2 )

c)" "None

Solution

In the given function f(x) = log(cosx) we know that the range of cosx is from [-1,1].

But the value of A in logA can not be negative or zero. Considering this in mind we can only have positive values of cosx.

We know that range of cosx remain positive only in 1st and 4th quadrant in x-y axis.

Hence domain of f(x) = log(cosx) should lie between ( 2npi - pi/2 , 2npi + pi/2 )