Question5. Find the phase relations for the following pairs of sinusoids: a) $u=6 \sin \left(30 t-40^{\circ}\right) V$ and $i=10 \sin (30 t-\pi / 3) \mathrm{mA}$ b) $u_{1}=-8 \sin \left(40 t-80^{\circ}\right) \mathrm{V}$ and $u_{2}=-10 \sin \left(40 t-50^{\circ}\right) \mathrm{V}$ c) $i_{1}=4 \cos \left(70 t-40^{\circ}\right) \mathrm{mA}$ and $i_{2}=-6 \cos \left(70 t+80^{\circ}\right) \mathrm{mA}$ d) $u=-4 \sin \left(45 t+5^{\circ}\right) V$ and $i=7 \cos \left(45 t+80^{\circ}\right) \mathrm{mA}$
Ans. a) $u$ leads $i$ by $20^{\circ}$; b) $u_{1}$ lags $u_{2}$ by $30^{\circ}$; c) $i_{1}$ leads $i_{2}$ by $60^{\circ}$; d) $u$ leads $i$ by $15^{\circ}$