To analyze the transformation to the parent function \( y = \cos x \) that results in \( y = -3.6 \cos x \), we can examine each option:
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A. The graph of the parent function is vertically compressed by 3.6.
- This statement is incorrect. A vertical compression would mean that the amplitude is less than 1. In this case, the amplitude is 3.6.
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B. The graph of the parent function is reflected across the x-axis.
- This statement is correct. The negative sign in front of the cosine function indicates that the graph is reflected across the x-axis.
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C. The amplitude of the parent function was changed from 0 to 3.6.
- This statement is incorrect. The amplitude of the cosine function is not changing from 0; it changes from 1 (the amplitude of the parent function) to 3.6. The amplitude is actually the absolute value of the coefficient in front of the cosine, which is 3.6 here.
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D. The graph of the parent function is vertically translated down 3.6 units.
- This statement is incorrect. There is no vertical translation in this transformation. The negative sign reflects the graph, but it does not translate it down; the entire graph is simply flipped over the x-axis.
Thus, the correct answer is:
B. The graph of the parent function is reflected across the x-axis.