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Ch. 1 - Trigonometric Functions
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161, 9780135440780, 9780136881117, 9780135440827, 9780135924891Non è quello che usi tu?Cambia libro di testo
Capitolo 2, Problema 43

Give all six trigonometric function values for each angle θ . Rationalize denominators when applicable.
sec θ = 5/4 , and θ is in quadrant IV

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Recall that the secant function is the reciprocal of the cosine function, so from \(\sec \theta = \frac{5}{4}\), we can find \(\cos \theta\) by taking the reciprocal: \(\cos \theta = \frac{4}{5}\).
Since \(\theta\) is in quadrant IV, cosine is positive and sine is negative in this quadrant. Use the Pythagorean identity \(\sin^2 \theta + \cos^2 \theta = 1\) to find \(\sin \theta\). Substitute \(\cos \theta = \frac{4}{5}\) and solve for \(\sin \theta\).
Determine the sign of \(\sin \theta\) based on the quadrant. Since \(\theta\) is in quadrant IV, \(\sin \theta\) should be negative. So, take the negative root from the previous step.
Find \(\tan \theta\) using the identity \(\tan \theta = \frac{\sin \theta}{\cos \theta}\). Substitute the values of \(\sin \theta\) and \(\cos \theta\) found earlier.
Calculate the remaining reciprocal functions: \(\csc \theta = \frac{1}{\sin \theta}\) and \(\cot \theta = \frac{1}{\tan \theta}\). Rationalize denominators if necessary.

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