Drawing an argand diagram of complex voltage

[joe007]

Homework Statement

draw an argand diagram of the complex voltage v at t=pi/1800, also how do i obtain the instantaneous voltage

Homework Equations

i = lcoswt

The Attempt at a Solution

well so far i have a straight line

 

[joe007]

also i know the projection on the horizontal axis represent the voltage and current
but what's d method of drawing it