Convert the following instantaneous currents to phasors, using \(\cos (\omega t)\) as the reference. Give your answers in both rectangular and polar form.

(a) \(i(t)=500 \sqrt{2} \cos (\omega t-30)\)

(b) \(i(t)=4 \sin (\omega t+30)\)

(c) \(i(t)=5 \cos (\omega t-15)+4 \sqrt{2} \sin (\omega t+30)\)