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At which values in the interval [tex][0, 2\pi)[/tex] will the functions [tex]f(x) = \cos 2x + 2[/tex] and [tex]g(x) = \sin x + 3[/tex] intersect?

A. [tex]x = \frac{\pi}{2}, \frac{7\pi}{6}, \frac{3\pi}{2}, \frac{11\pi}{6}[/tex]
B. [tex]x = \frac{\pi}{6}, \frac{\pi}{2}, \frac{5\pi}{6}, \frac{3\pi}{2}[/tex]
C. [tex]x = 0, \frac{\pi}{6}, \frac{5\pi}{6}, \pi[/tex]
D. [tex]x = 0, \pi, \frac{7\pi}{6}, \frac{11\pi}{6}[/tex]


Sagot :

To determine the values in the interval [tex]\([0, 2\pi)\)[/tex] at which the functions [tex]\( f(x) = \cos 2x + 2 \)[/tex] and [tex]\( g(x) = \sin x + 3 \)[/tex] intersect, we follow these steps:

1. Set up the equation [tex]\( f(x) = g(x) \)[/tex]:
[tex]\[ \cos 2x + 2 = \sin x + 3 \][/tex]

2. Simplify the equation:
[tex]\[ \cos 2x + 2 - \sin x - 3 = 0 \][/tex]
[tex]\[ \cos 2x - \sin x - 1 = 0 \][/tex]

3. Solve the equation for [tex]\( x \)[/tex] within the interval [tex]\([0, 2\pi)\)[/tex]:

This requires finding the points where the two functions are equal in the specified interval.

4. List the points of intersection:
After working through the solution, the calculated points of intersection are:
[tex]\[ 0, \pi, \frac{7\pi}{6}, \frac{11\pi}{6} \][/tex]

5. Verify if these points fall within the given interval [tex]\([0, 2\pi)\)[/tex]:
- [tex]\( 0 \)[/tex] is in [tex]\([0, 2\pi)\)[/tex]
- [tex]\( \pi \)[/tex] is in [tex]\([0, 2\pi)\)[/tex]
- [tex]\( \frac{7\pi}{6} \)[/tex] (which is approximately 3.66519) is in [tex]\([0, 2\pi)\)[/tex]
- [tex]\( \frac{11\pi}{6} \)[/tex] (which is approximately 5.75959) is in [tex]\([0, 2\pi)\)[/tex]

Therefore, the values of [tex]\(x\)[/tex] in the interval [tex]\([0, 2\pi)\)[/tex] at which the functions [tex]\( f(x) = \cos 2x + 2 \)[/tex] and [tex]\( g(x) = \sin x + 3 \)[/tex] intersect are:

[tex]\[ x = 0, \pi, \frac{7\pi}{6}, \frac{11\pi}{6} \][/tex]

Hence, the correct multiple-choice option is:
[tex]\[ \boxed{x = 0, \pi, \frac{7\pi}{6}, \frac{11\pi}{6}} \][/tex]