Using complete sentences, explain the key features of the graph of the cosine function.

The parent cosine function has the following key features, starting from the origin.

The equation of the function is y = cos(x)

The function starts with a maximum value at x = 0, which is 1. It then reduces to zero and then to its minimum value which -1 and then back to zero.This cycle continues as shown in the figure below.

So the sequence of change for a cosine function is {Maximum, Zero, Minimum, Zero, Maximum}

The period of cosine function is 2π, which means the cosine function will start repeating its values after a change of 2π in x values.