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Ch. 6 - Inverse Circular Functions and Trigonometric Equations
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161Not the one you use?Change textbook
Chapter 7, Problem 6.3.51

Solve each equation over the interval [0, 2π). Write solutions as exact values or to four decimal places, as appropriate.


sin x/2 - cos x/2 = 0

Verified step by step guidance
1
Start with the given equation: \(\sin \frac{x}{2} - \cos \frac{x}{2} = 0\).
Rearrange the equation to isolate one trigonometric function: \(\sin \frac{x}{2} = \cos \frac{x}{2}\).
Divide both sides by \(\cos \frac{x}{2}\) (assuming \(\cos \frac{x}{2} \neq 0\)) to get \(\tan \frac{x}{2} = 1\).
Solve for \(\frac{x}{2}\) by finding the angles where \(\tan \theta = 1\) within the interval for \(\frac{x}{2}\), which is \([0, \pi)\) because \(x \in [0, 2\pi)\).
Multiply the solutions for \(\frac{x}{2}\) by 2 to find the corresponding values of \(x\) in the interval \([0, 2\pi)\).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Trigonometric Equations

Trigonometric equations involve functions like sine and cosine and require finding all angle values that satisfy the equation within a given interval. Solving these often involves algebraic manipulation and applying identities to isolate the variable.
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Angle Division and Substitution

When the variable appears as a fraction of the angle (e.g., x/2), it is helpful to use substitution (such as letting t = x/2) to simplify the equation. This allows solving for t first, then converting back to x, ensuring solutions fit the original interval.
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Using Trigonometric Identities

Identities like sin A = cos A or sin A = cos(π/2 - A) help transform and simplify equations. Recognizing that sin θ = cos θ implies θ = π/4 + kπ enables finding exact solutions efficiently.
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Related Practice