Final answer:
The Nyquist frequency for the signal s(t)=2cos(20πt) is 20 Hz, calculated by doubling the signal's frequency of 10 Hz.
Step-by-step explanation:
The Nyquist frequency is the minimum sampling rate required to avoid aliasing and is equal to twice the maximum frequency component of the signal. For a sinusoidal signal s(t)=2cos(20πt), the maximum frequency component can be determined by the term 20π, which represents the angular frequency ω. Given that the angular frequency ω is equal to 2πf (where f is the frequency), we can calculate the frequency of the signal as f = ω/(2π) = (20π)/(2π) = 10 Hz. Therefore, the Nyquist frequency for this signal is 2 × 10 Hz = 20 Hz.