If cos x = k has exactly one solution in [0, 2 π], then write the value(s) of k.
As cos x = cos θ
Then x=2nπ ± θ
And it is said that it has exactly one solution.
So θ=0 and
=nπ
In the given interval taking n=1,x=π {n=0 is not possible as cos 0 = 1 not -1 but cos π is -1}