Which of the following functions illustrates a change in amplitude?

Question

Which of the following functions illustrates a change in amplitude?

 

a) y=tan2x

b)y=-2-cos(x-π)

c) y=-2cox6x

d)y=1+sinx

 

 

I think it is D....

Answer 1

Amplitude is the distance from the "peak to the trough" of a wave, in other words from top to bottom.

 

D is a sine curve where the whole graph is shifted up by the same amount.  So the peak-to-trough distance doesn't change. 

 

However, in C, the top of the wave is higher and the bottom is lower.  So the peak-to-trough distance DOES change.

 

So the answer is C