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The solution set of the equation 4 "sin"...

The solution set of the equation `4 "sin" theta "cos" theta- 2 "cos" theta -2sqrt(3) "sin" theta + sqrt(3) =0 " in the interval" (0, 2 pi)`, is

A

`{ (3pi)/(4), (7pi)/(4)}`

B

`{ (pi)/(3), (5pi)/(3)}`

C

`{ (3pi)/(4),pi, pi/3, (5pi)/(4)}`

D

`{ (pi)/(6), (5pi)/6, (11pi)/(6)}`

Text Solution

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The correct Answer is:
To solve the equation \( 4 \sin \theta \cos \theta - 2 \cos \theta - 2\sqrt{3} \sin \theta + \sqrt{3} = 0 \) in the interval \( (0, 2\pi) \), we can follow these steps: ### Step 1: Rearrange the Equation We start with the equation: \[ 4 \sin \theta \cos \theta - 2 \cos \theta - 2\sqrt{3} \sin \theta + \sqrt{3} = 0 \] ### Step 2: Factor the Equation We can factor out common terms. Notice that we can group the terms: \[ (4 \sin \theta \cos \theta - 2\sqrt{3} \sin \theta) + (-2 \cos \theta + \sqrt{3}) = 0 \] Now, we can factor out \( 2 \cos \theta \) from the first part and \( -\sqrt{3} \) from the second part: \[ 2 \cos \theta (2 \sin \theta - 1) - \sqrt{3} (2 \sin \theta - 1) = 0 \] This gives us: \[ (2 \sin \theta - 1)(2 \cos \theta - \sqrt{3}) = 0 \] ### Step 3: Set Each Factor to Zero Now we set each factor equal to zero: 1. \( 2 \sin \theta - 1 = 0 \) 2. \( 2 \cos \theta - \sqrt{3} = 0 \) ### Step 4: Solve for \( \theta \) **For the first equation:** \[ 2 \sin \theta - 1 = 0 \implies \sin \theta = \frac{1}{2} \] The solutions for \( \sin \theta = \frac{1}{2} \) in the interval \( (0, 2\pi) \) are: \[ \theta = \frac{\pi}{6}, \frac{5\pi}{6} \] **For the second equation:** \[ 2 \cos \theta - \sqrt{3} = 0 \implies \cos \theta = \frac{\sqrt{3}}{2} \] The solutions for \( \cos \theta = \frac{\sqrt{3}}{2} \) in the interval \( (0, 2\pi) \) are: \[ \theta = \frac{\pi}{6}, \frac{11\pi}{6} \] ### Step 5: Combine the Solutions Now we combine all the solutions we found: - From \( \sin \theta = \frac{1}{2} \): \( \theta = \frac{\pi}{6}, \frac{5\pi}{6} \) - From \( \cos \theta = \frac{\sqrt{3}}{2} \): \( \theta = \frac{\pi}{6}, \frac{11\pi}{6} \) The unique solutions in the interval \( (0, 2\pi) \) are: \[ \theta = \frac{\pi}{6}, \frac{5\pi}{6}, \frac{11\pi}{6} \] ### Final Answer Thus, the solution set of the equation is: \[ \left\{ \frac{\pi}{6}, \frac{5\pi}{6}, \frac{11\pi}{6} \right\} \]
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