Final answer:
The amplitude of the function y = 21cos(5x) is 21, as the amplitude is represented by the coefficient in front of the cosine function.
Step-by-step explanation:
The amplitude of a trigonometric function like y = \(\frac{1}{21}\)cos(5x) can be determined by looking at the coefficient in front of the cosine function. In a standard cosine function of the form y = A cos(Bx), the amplitude is represented by the absolute value of A. Therefore, for the given function y = \(\frac{1}{21}\)cos(5x), the amplitude is simply the coefficient 21.