The formula as given is a little confusing, what with that [V] term dangling out there. If we assume t in seconds, and [V] just some arbitrary constant, you could express your answer in terms of [V]. All you really have to do is find the value of the sine function for t=.0005 seconds, which turns out to be .707. Thus the answer would be 3.535[V], but again I have no idea how to interpret the [V] term...
For t=.0005, the argument of the sine function evaluates to 0.5pi + pi/4 = 3*pi/4. Since 2pi radians = 360 degrees, the phase is 135 degrees. This is consistent with the value of the sine function, 0.707, which is the value of a sine function at any multiple of 45 degrees.
Was [V] originally written as |V|, by any chance? That would make sense.