Answer:
6
Explanation:
The period of a sine or cosine graph is the length of x-values that it takes to curve up from the axis of symmetry to the crest, down to the trough, then back up to the axis of symmetry.
In this case, the axis of symmetry is the x-axis, or y = 0.
We can see that the graph starts going up to the crest at:
x =

and it comes up from the trough at:
x =

We can calculate the period of the function by subtracting these values.

So, the period of this sine or cosine graph is 6.