Really scratchin my head with this little lot and would be extremely grateful for a hand working it all out....

An a.c voltage, V, comprises of a fundamental voltage of 100 V rms at a
frequency of 120 Hz, a 3rd harmonic which is 20% of the fundamental, a
5th harmonic which is 10% of the fundamental and at a phase angle of
1.2 radians lagging.
(i) Write down an expression for the voltage waveform.
(ii) Sketch the waveforms of the harmonic components.
(iii) Determine the voltage at 20 ms.

(iv) Given an ideal V = 100 V rms, what is the percentage error at 20 ms ?