What is the actual value, in volts, of the voltage across a wall plug at t = .01, .02 .05 and .1 sec., if the voltage is given by this expression.

Note, you should know the frequency of the voltage appearing at the wall plug.  If you don't, it is 60 Hz, and that is the standard power frequency in the U. S.  In Europe and elsewhere, the power frequency might be 50 Hz, or sometimes even 25 Hz.