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Ch. 2 - Graphs of the Trigonometric Functions; Inverse Trigonometric Functions
Blitzer - Trigonometry 3rd Edition
Blitzer3rd EditionTrigonometryISBN: 9780137316601Not the one you use?Change textbook
Chapter 2, Problem 3

Find the exact value of each expression. sin⁻¹ √2/2

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1
Recognize that the expression involves the inverse sine function, written as \(\sin^{-1}\), which means we are looking for an angle \(\theta\) such that \(\sin(\theta) = \frac{\sqrt{2}}{2}\).
Recall the range of the inverse sine function \(\sin^{-1}(x)\), which is \([-\frac{\pi}{2}, \frac{\pi}{2}]\) or \([-90^\circ, 90^\circ]\), so the angle we find must lie within this interval.
Identify the common angles where sine values are known, especially those involving \(\frac{\sqrt{2}}{2}\). For example, \(\sin(\frac{\pi}{4}) = \frac{\sqrt{2}}{2}\).
Since \(\sin(\frac{\pi}{4}) = \frac{\sqrt{2}}{2}\) and \(\frac{\pi}{4}\) is within the range of \(\sin^{-1}\), conclude that \(\sin^{-1}(\frac{\sqrt{2}}{2}) = \frac{\pi}{4}\).
Express the final answer as the exact angle in radians or degrees, depending on the context of the problem.

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Key Concepts

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

Inverse Sine Function (sin⁻¹ or arcsin)

The inverse sine function, denoted as sin⁻¹ or arcsin, returns the angle whose sine value is a given number. It is defined for inputs between -1 and 1 and outputs angles typically in the range [-π/2, π/2] or [-90°, 90°]. Understanding this helps find the angle corresponding to a specific sine value.
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Exact Values of Sine for Special Angles

Certain angles have well-known sine values expressed in exact terms, such as √2/2 for 45° (π/4 radians). Recognizing these special angles allows you to determine the exact angle without a calculator, which is essential for solving inverse trigonometric expressions exactly.
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Domain and Range Restrictions of Inverse Trigonometric Functions

Inverse trigonometric functions have restricted domains and ranges to ensure they are functions. For sin⁻¹, the input must be between -1 and 1, and the output angle lies between -90° and 90°. This restriction ensures a unique solution when finding the angle from a sine value.
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