We need to get this in a simpler form. In this one, notice that the angles in the brackets are not the same!
We must simplify them first so they are the same.

Now we can express i in the form R sin(t + α).
So
2 sin t − 1.732 cos t = 2.646 sin(t − 0.714)
So the maximum value of this is 2.646 A.
To find when this occurs, we need to solve:
2.646 sin(t − 0.714) = 2.646
i.e. sin(t − 0.714) = 1
t − 0.714 = π/2
t = 2.29
So t = 2.29 s is the time when the maximum is first reached.