The period of the function f (x) = cos x2 is

Let f (T + x) = f (x) ⇒ cos (T + x)2 = cos x2⇒ (T + x)2 = 2nπ ± x2Clearly, from here, no positive value of T independent of x is possible because x2 on R.H.S. can be cancelled only when T = 0.∴ f (x) is a non periodic function.