Find all solutions of each equation. 3 sin θ + 5 = ﹣2 sin θ
Ch. 3 - Trigonometric Identities and Equations

Chapter 3, Problem 25
Exercises 25–38 involve equations with multiple angles. Solve each equation on the interval [0, 2𝝅). sin 2x = √3 / 2
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Start by writing down the given equation: \(\sin 2x = \frac{\sqrt{3}}{2}\).
Recall that \(\sin \theta = \frac{\sqrt{3}}{2}\) at specific standard angles. Identify all angles \(\theta\) in the interval \([0, 2\pi)\) where this is true. These angles are \(\theta = \frac{\pi}{3}\) and \(\theta = \frac{2\pi}{3}\).
Since the equation involves \$2x\(, set \(2x = \frac{\pi}{3} + 2k\pi\) and \(2x = \frac{2\pi}{3} + 2k\pi\), where \)k$ is any integer, to account for the periodicity of the sine function.
Solve each equation for \(x\) by dividing both sides by 2: \(x = \frac{\pi}{6} + k\pi\) and \(x = \frac{\pi}{3} + k\pi\).
Find all values of \(x\) within the interval \([0, 2\pi)\) by substituting integer values of \(k\) (such as \(k=0\) and \(k=1\)) into the expressions for \(x\).

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Double-Angle Identities
Double-angle identities express trigonometric functions of multiples of an angle in terms of single angles. For example, sin(2x) = 2 sin x cos x. These identities help simplify and solve equations involving multiple angles like sin 2x.
Recommended video:
Double Angle Identities
Solving Trigonometric Equations
Solving trigonometric equations involves isolating the trigonometric function and finding all angle solutions within a given interval. This often requires using inverse functions and considering the periodicity of sine, cosine, or tangent.
Recommended video:
How to Solve Linear Trigonometric Equations
Unit Circle and Interval Constraints
The unit circle helps visualize sine and cosine values for angles between 0 and 2π. Understanding the interval [0, 2π) is crucial to find all valid solutions within one full rotation, considering the periodic nature of trigonometric functions.
Recommended video:
Introduction to the Unit Circle
Related Practice
Textbook Question
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Use one or more of the six sum and difference identities to solve Exercises 13–54. In Exercises 13–24, find the exact value of each expression. tan ( 5𝝅/3 ﹣ 𝝅/4)
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