Trả lời bởi giáo viên
Đáp án đúng: d
Ta có:
\({u_{AM}} = {U_{0{\rm{A}}M}}\cos \omega t\)
\({u_{MN}} = {U_{0MN}}\cos \left( {\omega t + \frac{\pi }{2}} \right)\)
\({u_{NB}} = {U_{0NB}}\cos \left( {\omega t - \frac{\pi }{2}} \right)\)
\( \Rightarrow {u_{AB}} = {u_{AM}} + {u_{MN}} + {u_{NB}}\)
\( \Rightarrow U_{AB}^2 = U_{AM}^2 + {\left( {{U_{MN}} - {U_{NB}}} \right)^2}\)
