A.\(u = 40co{\rm{s}}\left( {100\pi t + \frac{\pi }{4}} \right)\left( V \right)\)
B.\(u = 40co{\rm{s}}\left( {100\pi t - \frac{\pi }{4}} \right)\left( V \right)\)
C.\(u = 40\sqrt 2 co{\rm{s}}\left( {100\pi t - \frac{\pi }{4}} \right)\left( V \right)\)
D.\(u = 40\sqrt 2 co{\rm{s}}\left( {100\pi t + \frac{\pi }{4}} \right)\left( V \right)\)

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