Answer: C. [tex]\pi[/tex]
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Explanation:
The x intercept always occurs when y = 0.
Use the unit circle to determine that [tex]\cos(\theta) = 0[/tex] when [tex]\theta = \frac{\pi}{2} \text{ and } \theta = \frac{3\pi}{2}[/tex]
So if [tex]x = \pi[/tex], then we have
[tex]y = \cos\left(\frac{1}{2}x\right)\\\\y = \cos\left(\frac{x}{2}\right)\\\\y = \cos\left(\frac{\pi}{2}\right)\\\\y = 0\\\\[/tex]
which shows us that [tex](\pi, 0)[/tex] is the location of one of the infinitely many x intercepts for this function.
