Phasor representation of AC voltage and current.
I\,=\,5\angle{0^o}\,=\,5\,+\,j0\,A
V\,=\,100\angle{30^o}\,=\,86.6\,+\,j50\,V
in general
V\,=\,A\angle{\theta^o}\,=\,A cos{\theta}\,+\,jA sin{\theta}\,V
and similarly for I
It is assumed that the angular frequency \omega is...