Answer:
8
Explanation:
You want the period of a sinusoidal function that has a graph with peaks at x=1 and x=9.
Period
The period is the difference between x-values where the function repeats itself. Typically, we can determine the period from corresponding recognizable features of the graph.
Here, the graph has peaks at x=1 and x=9. The period is the difference between these x-values:
period = 9 - 1 = 8
The period of the function is 8 units.
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Additional comment
In more formal terms, the period p of a function is the smallest value of p such that f(x -p) = f(p).