Answer:
2cos(3x)
Step-by-step explanation:
If the function were just cos(x), then the second peak would happen at 2π. Instead though, it happen 2π / 3. That means that the coefficient of x must be 3.
At zero, we see a peak of the curve, so we're dealing with a cos function, that peak happens at (0, 2), so the coefficient of the function is 2.
That tells us that the function graphed here must be 2cos(3x).
