Final answer:
The given signal u(t) = 5cos(1800πt) is an example of an amplitude modulated (AM) signal. In AM modulation, the amplitude of a carrier wave is varied in accordance with an audio signal, resulting in a wave with constant frequency but varying amplitude.
Step-by-step explanation:
The given signal u(t) = 5cos(1800πt) is an example of an amplitude modulated (AM) signal. In AM modulation, the amplitude of a carrier wave is varied in accordance with an audio signal, resulting in a wave with constant frequency but varying amplitude.
The information conveyed by this signal is encoded in the variations of the amplitude. In the case of u(t) = 5cos(1800πt), the audio signal being conveyed would cause the amplitude of the carrier wave to vary between -5 and +5. This can be visualized by plotting the waveform of the signal over time.
AM modulation is commonly used in commercial AM radio broadcasting, where the amplitude variations carry the audio signal being broadcasted. The signal u(t) = 5cos(1800πt) represents one possible modulation scheme in AM radio.