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Ch. 7 - Transcendental Functions
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Non è quello che usi tu?Cambia libro di testo
Capitolo 7, Problema 7.6.4b

Use reference triangles in an appropriate quadrant to find the angles in Exercises 1–8.
4. b. arcsin(-1/√2)

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Recall that the function \(\arcsin(x)\) gives the angle \(\theta\) whose sine is \(x\), with the range of \(\arcsin\) restricted to \([-\frac{\pi}{2}, \frac{\pi}{2}]\) (Quadrants IV and I).
Identify the value inside the \(\arcsin\): here it is \(-\frac{1}{\sqrt{2}}\). Recognize that \(\sin\left(\frac{\pi}{4}\right) = \frac{1}{\sqrt{2}}\), so the reference angle is \(\frac{\pi}{4}\).
Since the sine value is negative, and \(\arcsin\) outputs angles in \([-\frac{\pi}{2}, \frac{\pi}{2}]\), the angle must be in Quadrant IV where sine is negative.
Use the reference triangle in Quadrant IV to express the angle as \(-\frac{\pi}{4}\), because sine of \(-\frac{\pi}{4}\) is \(-\frac{1}{\sqrt{2}}\).
Therefore, the angle \(\theta = \arcsin\left(-\frac{1}{\sqrt{2}}\right)\) corresponds to \(-\frac{\pi}{4}\) within the principal range of \(\arcsin\).

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