a) Utot = 1.98 microJ
b) qmax = 5.56 microC
c) imax = 12.6 mA
d) phase angle is -46.9 degrees
Why negative? We found that the cosine of the phase angle should be 0.68; thus the phase angle may be +/- 46.9 degrees. The sign is chosen depending on whether the capacitor is charging or discharging. To decide, look at the time derivative of the charge at t=0, which is proportional to the negative of the sine of the phase angle. For a charging capacitor, this derivative should be positive; thus the choice of -46.9 degrees.
e) phase angle is +46.9 degrees