$\"\"$

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Observe the graph:

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It is a cosine function graph.

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The general form of cosine function is $\"\"$ .

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The maximum value is $\"\"$ occurs at $\"\"$ .

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Amplitude of the graph is $\"\"$ .

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The period $\"\"$ .

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The period of the graph is $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ .

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Substitute $\"\"$ and $\"\"$ in $\"\"$ .

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$\"\"$

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Rewrite the function.

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$\"\"$ .

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Therefore,the choice $\"\"$ is correct.

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$\"\"$

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The choice $\"\"$ is correct.