Finding voltage across elements in phasor diagram,

[checkedcherry]

Finding voltage across elements in phasor diagram, URGENT!

Hi there, first time posting here, just caught up on a question with no worked solutions and it's driving me crazy!

I've attached the question below,and the answer to b is v(t)= 5cos(2t-112).
I can do part a but am struggling on part b nothing I try seems to come up with 112 degrees :(

Anyway, here's my (very poor) attempt:

I found the current to be
1.386 < -56.5 degrees i.e 1.386 cos (2t-56.5)

and then tried to find voltage across the capacitor using V=IZ to get 4.14cos(2t+33.5)
which didn't seem right...so can anyone point me in the right direction?

Thanks in advance!

 

[SirAskalot]

Clue: RMS value (root mean square) vs. peak value...

1.386 < -56.5 degrees ≠ 1.386 cos (2t-56.5)