1. What is the phase sequence of each of the following sets of voltages? \text { a) } v_{a}=180 \cos \left(\omega t+27^{\circ}\right) V, v_{b}=180 \cos \left(\omega t+147^{\circ}\right) V, v_{c}=180 \cos

\left(\omega t-93^{\circ}\right) V \text { b) } v_{a}=4160 \cos \left(\omega t-18^{\circ}\right) V, v_{b}=4160 \cos \left(\omega t-138^{\circ}\right) V, v_{c}=4160 \cos \left(\omega t+102^{\circ}\right) V