Answer :

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You're right, let's determine the equation of the given trigonometric graph based on its key characteristics:

1. **Amplitude**: The amplitude is the maximum value of the cosine function from its centerline. Observing the graph, the maximum value is 3 and the minimum value is -3. Hence, the amplitude $A$ is 3.

2. **Period**: The period of the cosine function is the length of one complete cycle. In the graph, one cycle is completed from $-\pi$ to $\pi$, so the period $P$ is $2\pi$.

3. **Phase Shift**: The graph does not appear to be horizontally shifted, as it starts at its maximum at $x = 0$. Therefore, the phase shift $C$ is 0.

4. **Vertical Shift**: The centerline of the graph appears to be at $y = 0$, indicating no vertical shift. Therefore, the vertical shift $D$ is 0.

Given these characteristics, the equation of the cosine function can be written as:

$y = A \cos \left( \frac{2\pi}{P} x \right) + D$

Substituting the values, we get:

$y = 3 \cos(x) + 0$

$y = 3 \cos(x)$

Therefore, the equation of the given trigonometric graph is $y = 3 \cos(x)$.