Which of the following functions illustrates a change in amplitude?

a. y = 3cos4x
b. y = 1+sinx
c. y = -2-cos(x - pi)
d. y = tan2x

Correct option is A.          

Step-by-step explanation:

Given the following functions we have to choose the option which illustrates a change in amplitude.

Multiplying a sine or cosine function by a constant changes the graph of the parent function i.e results in change in the amplitude of function. Amplitude is the measure of distance from the sinusoidal axis to the maximum or the minimum.

Option A:  y = 3cos4x

The parent function is f(x) = cos x.

The amplitude of function changes from 1 to 3.

Option B:  y = 1+sinx

The parent function is f(x) = sin x

The amplitude remains same i.e 1

Option C: y = -2-cos(x - pi)

Here also remains same.

Option D: y = tan 2x

The tangent function does not have an amplitude because it has no maximum or minimum value.

Hence, correct option is A.