Hi everyone

I really dont know how to start this questions, please help me. Thank you in advance for all your help & support.

Determine if each of the following CT signals is periodic. If periodic find it period.

a) x(t)=2sin(10$\displaystyle \pi$t-30degrees)

b) x(t) = 2 cos ($\displaystyle \sqrt$2$\displaystyle \pi$t)

c)x(t) = 2 sin ($\displaystyle \sqrt$$\displaystyle \pi$t)

d) x(t) = 2 cos (t+ 60degrees)