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Solve for [tex]\( x \)[/tex]:
[tex]\[ 2 \cos^2 x + \sin x - 2 = 0 \][/tex]


Sagot :

Certainly! To solve the given trigonometric equation [tex]\(2 \cos^2 x + \sin x - 2 = 0\)[/tex], follow these steps:

1. Express [tex]\(\cos^2 x\)[/tex] in terms of [tex]\(\sin x\)[/tex]:
Using the Pythagorean identity, we know that:
[tex]\[ \cos^2 x = 1 - \sin^2 x \][/tex]

2. Substitute [tex]\(\cos^2 x\)[/tex] into the equation:
Replacing [tex]\(\cos^2 x\)[/tex] with [tex]\(1 - \sin^2 x\)[/tex], the equation becomes:
[tex]\[ 2(1 - \sin^2 x) + \sin x - 2 = 0 \][/tex]

3. Simplify the equation:
Distribute the 2 and combine like terms:
[tex]\[ 2 - 2\sin^2 x + \sin x - 2 = 0 \][/tex]
[tex]\[ -2 \sin^2 x + \sin x = 0 \][/tex]

4. Factor the equation:
Factor out a [tex]\(\sin x\)[/tex] from the left-hand side:
[tex]\[ \sin x (-2 \sin x + 1) = 0 \][/tex]

5. Set each factor to zero and solve:
We have two factors to solve:
[tex]\[ \sin x = 0 \][/tex]
and
[tex]\[ -2 \sin x + 1 = 0 \][/tex]

6. Solve [tex]\(\sin x = 0\)[/tex]:
[tex]\[ x = 0, \pi, 2\pi, \ldots \][/tex]

7. Solve [tex]\(-2 \sin x + 1 = 0\)[/tex]:
Rearrange the equation:
[tex]\[ \sin x = \frac{1}{2} \][/tex]
The solutions for [tex]\(\sin x = \frac{1}{2}\)[/tex] within one period [tex]\([0, 2\pi)\)[/tex] are:
[tex]\[ x = \frac{\pi}{6}, \frac{5\pi}{6} \][/tex]

8. Combine all solutions:
The general solutions combining the periodic nature of the sine function are:
[tex]\[ x = 0, \pi, \frac{\pi}{6}, \frac{5\pi}{6}, 2\pi, \ldots \][/tex]

Since we are asked for the primary solutions within one period [tex]\([0, 2\pi)\)[/tex], the solutions to the equation [tex]\(2 \cos^2 x + \sin x - 2 = 0\)[/tex] are:
[tex]\[ x = 0, \frac{\pi}{6}, \frac{5\pi}{6} \][/tex]

Thus, the solutions are:

[tex]\[ \boxed{0, \frac{\pi}{6}, \frac{5\pi}{6}} \][/tex]