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What are the solutions of \( \sin 2 \theta=\sqrt{2} \cos \theta \) on the interval \( [0,2 \pi) \) ? Select 4 choice(s) \( \square \frac{\pi}{4} \) \( \square \frac{3 \pi}{2} \) \( \square \)

Ask by Owen Craig. in the United Arab Emirates
Feb 26,2025

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Answer

The solutions are \( \frac{\pi}{4} \), \( \frac{3\pi}{4} \), \( \frac{\pi}{2} \), and \( \frac{3\pi}{2} \).

Solution

To solve sin 2θ = √2·cos θ on the interval [0, 2π), start by using the double-angle formula for sine:   sin 2θ = 2 sin θ cos θ So the equation becomes:   2 sin θ cos θ = √2 · cos θ Step 1. Bring all terms to one side:   2 sin θ cos θ − √2 · cos θ = 0 Step 2. Factor out cos θ:   cos θ (2 sin θ − √2) = 0 Now, set each factor equal to zero. Case 1: cos θ = 0  • cos θ = 0 when θ = π/2 and θ = 3π/2. Case 2: 2 sin θ − √2 = 0  • Solve for sin θ:   2 sin θ = √2 ⟹ sin θ = √2/2  • sin θ = √2/2 on [0, 2π) gives:   θ = π/4 and θ = 3π/4. Thus, the solutions on [0, 2π) are:   θ = π/4, 3π/4, π/2, 3π/2 These are the four solutions to the equation. Answer Choices:  □ π/4  □ 3π/2  □ π/2  □ 3π/4

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To solve the equation \( \sin 2\theta = \sqrt{2} \cos \theta \), we can use the double angle identity for sine, which gives us \( \sin 2\theta = 2 \sin \theta \cos \theta \). This transforms the equation into: \[ 2 \sin \theta \cos \theta = \sqrt{2} \cos \theta. \] Assuming \( \cos \theta \neq 0 \), we can divide both sides by \( \cos \theta \): \[ 2 \sin \theta = \sqrt{2}. \] This simplifies to: \[ \sin \theta = \frac{\sqrt{2}}{2}. \] The solutions to this equation are \( \theta = \frac{\pi}{4} \) and \( \theta = \frac{3\pi}{4} \) within the interval \( [0, 2\pi) \). Now, let’s also consider the condition \( \cos \theta = 0 \). This condition gives us: \[ \theta = \frac{\pi}{2} \text{ and } \theta = \frac{3\pi}{2}. \] Combining both scenarios, the final solutions for the equation \( \sin 2\theta = \sqrt{2} \cos \theta \) on the interval \( [0, 2\pi) \) are: - \( \frac{\pi}{4} \) - \( \frac{3\pi}{4} \) - \( \frac{\pi}{2} \) - \( \frac{3\pi}{2} \) Thus, you can select: \( \square \frac{\pi}{4} \) \( \square \frac{3 \pi}{4} \) \( \square \frac{\pi}{2} \) \( \square \frac{3 \pi}{2} \)

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