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Find all solutions of the equation in the interval [tex]\([0, 2\pi)\)[/tex].

[tex]\[
\cot^2 x + 3 \csc x = -3
\][/tex]

Write your answer in radians in terms of [tex]\(\pi\)[/tex]. If there is more than one solution, separate them with commas.

[tex]\[
x = \boxed{\pi} \boxed{\ , \ldots}
\][/tex]


Sagot :

Sure, let's solve the equation:

[tex]\[ \cot^2(x) + 3 \csc(x) = -3 \][/tex]

Step 1: Use trigonometric identities. Recall that [tex]\(\cot(x) = \frac{\cos(x)}{\sin(x)}\)[/tex] and [tex]\(\csc(x) = \frac{1}{\sin(x)}\)[/tex]. Therefore, we can rewrite the equation in terms of sine and cosine:

[tex]\[ \left(\frac{\cos(x)}{\sin(x)}\right)^2 + 3 \frac{1}{\sin(x)} + 3 = 0 \][/tex]

Step 2: Simplify the equation. Let [tex]\( u = \csc(x) = \frac{1}{\sin(x)} \)[/tex]. Then, [tex]\(\cot^2(x) = \csc^2(x) - 1\)[/tex], so the equation becomes:

[tex]\[ (u^2 - 1) + 3u + 3 = 0 \][/tex]

Step 3: Combine like terms:

[tex]\[ u^2 + 3u + 2 = 0 \][/tex]

Step 4: Factor the quadratic equation:

[tex]\[ (u + 1)(u + 2) = 0 \][/tex]

Step 5: Solve for [tex]\( u \)[/tex]:

[tex]\[ u + 1 = 0 \quad \text{or} \quad u + 2 = 0 \][/tex]

[tex]\[ u = -1 \quad \text{or} \quad u = -2 \][/tex]

Since [tex]\( u = \csc(x) = \frac{1}{\sin(x)} \)[/tex], we solve for [tex]\(\sin(x)\)[/tex]:

1. For [tex]\( u = -1 \)[/tex]:

[tex]\[ \frac{1}{\sin(x)} = -1 \implies \sin(x) = -1 \][/tex]

2. For [tex]\( u = -2 \)[/tex]:

[tex]\[ \frac{1}{\sin(x)} = -2 \implies \sin(x) = -\frac{1}{2} \][/tex]

Step 6: Determine the angles in the interval [tex]\([0, 2\pi)\)[/tex] for these sine values.

1. For [tex]\(\sin(x) = -1\)[/tex]:

[tex]\[ x = \frac{3\pi}{2} \][/tex]

2. For [tex]\(\sin(x) = -\frac{1}{2}\)[/tex]:

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

Therefore, the solutions to the equation [tex]\(\cot^2(x) + 3\csc(x) = -3\)[/tex] in the interval [tex]\([0, 2\pi)\)[/tex] are:

[tex]\[ x = \frac{7\pi}{6}, \frac{11\pi}{6}, \frac{3\pi}{2} \][/tex]