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Ch. 3 - Trigonometric Identities and Equations
Blitzer - Trigonometry 3rd Edition
Blitzer3rd EditionTrigonometryISBN: 9780137316601Non è quello che usi tu?Cambia libro di testo
Capitolo 3, Problema 64c

In Exercises 57–64, find the exact value of the following under the given conditions: c. tan (α + β), sin α = 5/6 , 𝝅/2 < α < 𝝅 , and tan β = 3/7 , 𝝅 < β < 3𝝅/2 .

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Identify the given information: \( \sin \alpha = \frac{5\pi}{6} \) with \( \frac{3\pi}{2} < \alpha < \pi \), and \( \tan \beta = \frac{7}{2} \) with \( \pi < \beta < \frac{3\pi}{2} \). Note that the interval for \( \alpha \) seems inconsistent since \( \frac{3\pi}{2} > \pi \). Verify the correct interval for \( \alpha \) before proceeding.
Recall the formula for the tangent of a sum: \(\tan(\alpha + \beta) = \frac{\tan \alpha + \tan \beta}{1 - \tan \alpha \tan \beta}\)
Find \( \tan \alpha \) using the given \( \sin \alpha \) and the Pythagorean identity. Since \( \sin \alpha = \frac{5\pi}{6} \), use: \(\cos \alpha = \pm \sqrt{1 - \sin^2 \alpha}\) Determine the sign of \( \cos \alpha \) based on the quadrant of \( \alpha \). Then calculate \( \(\tan\) \(\alpha\) = \(\frac{\sin \alpha}{\cos \alpha}\)$.
Use the given \( \tan \beta = \frac{7}{2} \) directly, noting the sign of \( \tan \beta \) based on the quadrant of \( \beta \).
Substitute \( \tan \alpha \) and \( \tan \beta \) into the tangent sum formula: \(\tan(\alpha + \beta) = \frac{\tan \alpha + \tan \beta}{1 - \tan \alpha \tan \beta}\) Simplify the expression to find the exact value.

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