Suppose we have a circuit in which the voltage is $v_{1}(t)=10 \cos \left(\omega t-30^{\circ}\right) \mathrm{V}$. Furthermore
the current $i_{1}(t)$ has an rms value of 10 A and $\operatorname{lag}_{5} v_{1}(t)$ by $40^{\circ},$ (The current and the volt ago have the same frequency.) Draw a phasor diagram and write an expression for $i_{1}(t)$ of the form $I_{m} \cos (\omega t+\theta)$