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Ch. 6 - Inverse Circular Functions and Trigonometric Equations
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161, 9780135440780, 9780136881117, 9780135440827, 9780135924891Non è quello che usi tu?Cambia libro di testo
Capitolo 7, Problema 6.3.47

Solve each equation (x in radians and θ in degrees) for all exact solutions where appropriate. Round approximate answers in radians to four decimal places and approximate answers in degrees to the nearest tenth. Write answers using the least possible nonnegative angle measures.


2 - sin 2θ = 4 sin 2θ

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Start by rewriting the given equation: \(2 - \sin 2\theta = 4 \sin 2\theta\).
Combine like terms by adding \(\sin 2\theta\) to both sides to isolate the sine term: \(2 = 4 \sin 2\theta + \sin 2\theta\) which simplifies to \(2 = 5 \sin 2\theta\).
Solve for \(\sin 2\theta\) by dividing both sides by 5: \(\sin 2\theta = \frac{2}{5}\).
Find the general solutions for \(2\theta\) by using the inverse sine function: \(2\theta = \sin^{-1}\left(\frac{2}{5}\right)\) and also consider the second solution in the range \([0, 2\pi)\), which is \(2\theta = \pi - \sin^{-1}\left(\frac{2}{5}\right)\).
Divide all solutions for \(2\theta\) by 2 to solve for \(\theta\), then express the answers in radians and degrees. For approximate answers, round radians to four decimal places and degrees to the nearest tenth. Also, write the solutions using the least possible nonnegative angle measures.

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Double-angle identities express trigonometric functions of 2θ in terms of θ, such as sin(2θ) = 2 sin θ cos θ. Recognizing and using these identities helps simplify equations and find solutions more efficiently.
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Understanding the difference between radians and degrees, and converting between them, is essential. Solutions must be expressed in the correct units, rounded appropriately, and within the specified interval, often using the least nonnegative angle measure.
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