Which of the following functions is periodic?

Which of the following function is periodic?

Which of the following function is periodic ?

Which of the following function is periodic ?

Which of the following function is periodic? sgn(e^(-x))x>0

Which of the following function is periodic with fundamental period pi ?

Which of the following function is periodic with fundamental period pi ?

Which of the following functions are periodic? f(x)={|sgn(x)|,x!=01,x=0

Which of the following function is a periodic function ?f(x)=sin((1)/(x));x!=0

Which of the following function is a periodic function? ( i f(x)=sin{x};{.}= fractional part of x(ii)f(x)=sin[x];[.]= greatest integer function ( iii) f(x)=log[x];[.]= greatest integer function (iv) f(x)=(sin x)/(x);x!=0

Which of the following functions has period pi ?