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How many solutions does the equation [tex]\(\sin(4x) = \frac{1}{2}\)[/tex] have on the interval [tex]\((0, 2\pi)\)[/tex]?

Answer here: [tex]\(\square\)[/tex]


Sagot :

First, let's understand the problem we are dealing with: solving the equation [tex]\(\sin(4x) = \frac{1}{2}\)[/tex] within the interval [tex]\((0, 2\pi)\)[/tex].

1. Identifying Basic Solutions:
The equation [tex]\(\sin(\theta) = \frac{1}{2}\)[/tex] has specific angles that satisfy it. We know that:
[tex]\[ \theta = \frac{\pi}{6} + 2k\pi \quad \text{and} \quad \theta = \frac{5\pi}{6} + 2k\pi \][/tex]
where [tex]\(k\)[/tex] is any integer.

2. Relating [tex]\(\theta\)[/tex] to [tex]\(4x\)[/tex]:
We rewrite the given equation in terms of [tex]\(\theta\)[/tex]:
[tex]\[ 4x = \frac{\pi}{6} + 2k\pi \quad \text{and} \quad 4x = \frac{5\pi}{6} + 2k\pi \][/tex]

3. Solving for [tex]\(x\)[/tex]:
To find [tex]\(x\)[/tex], we divide both sides by 4:
[tex]\[ x = \frac{\pi}{24} + \frac{k\pi}{2} \quad \text{and} \quad x = \frac{5\pi}{24} + \frac{k\pi}{2} \][/tex]

4. Determining Valid [tex]\(x\)[/tex] Values Within the Interval [tex]\((0, 2\pi)\)[/tex]:
We need to find [tex]\(x\)[/tex] values that lie within the interval [tex]\((0, 2\pi)\)[/tex]. We test various integer values of [tex]\(k\)[/tex].

- For [tex]\(\frac{\pi}{24} + \frac{k\pi}{2}\)[/tex]:
[tex]\[ \begin{aligned} &k = 0:\quad x = \frac{\pi}{24} \\ &k = 1:\quad x = \frac{\pi}{24} + \frac{\pi}{2} = \frac{13\pi}{24} \\ &k = 2:\quad x = \frac{\pi}{24} + \pi = \frac{25\pi}{24} \\ &k = 3:\quad x = \frac{\pi}{24} + \frac{3\pi}{2} = \frac{37\pi}{24} \end{aligned} \][/tex]
All these values are within [tex]\((0, 2\pi)\)[/tex].

- For [tex]\(\frac{5\pi}{24} + \frac{k\pi}{2}\)[/tex]:
[tex]\[ \begin{aligned} &k = 0:\quad x = \frac{5\pi}{24} \\ &k = 1:\quad x = \frac{5\pi}{24} + \frac{\pi}{2} = \frac{17\pi}{24} \\ &k = 2:\quad x = \frac{5\pi}{24} + \pi = \frac{29\pi}{24} \\ &k = 3:\quad x = \frac{5\pi}{24} + \frac{3\pi}{2} = \frac{41\pi}{24} \end{aligned} \][/tex]
All these values are within [tex]\((0, 2\pi)\)[/tex].

5. Counting the Solutions:
Combining all the valid [tex]\(x\)[/tex] values, we have 8 solutions in total for the given equation in the specified interval.

Thus, the number of solutions to the equation [tex]\(\sin(4x) = \frac{1}{2}\)[/tex] within the interval [tex]\((0, 2\pi)\)[/tex] is:
[tex]\[ \boxed{8} \][/tex]