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Ch. 2 - Graphs of the Trigonometric Functions; Inverse Trigonometric Functions
Blitzer - Trigonometry 3rd Edition
Blitzer3rd EditionTrigonometryISBN: 9780137316601Non è quello che usi tu?Cambia libro di testo
Capitolo 2, Problema 39

In Exercises 39–54, find the exact value of each expression, if possible. Do not use a calculator. sin(sin⁻¹ 0.9)

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Recognize that the expression is \( \sin(\sin^{-1}(0.9)) \). The function \( \sin^{-1} \) (also called arcsin) is the inverse of the sine function, which means it 'undoes' the sine function within its domain.
Recall the property of inverse functions: for any value \( x \) in the domain of \( \sin^{-1} \), \( \sin(\sin^{-1}(x)) = x \). This holds true because \( \sin^{-1}(x) \) gives the angle whose sine is \( x \).
Check that the input value \( 0.9 \) is within the domain of \( \sin^{-1} \), which is \( [-1, 1] \). Since \( 0.9 \) is within this range, the property applies directly.
Therefore, the expression simplifies directly to \( 0.9 \) without further calculation.
Summarize that \( \sin(\sin^{-1}(0.9)) = 0.9 \) because the sine and arcsine functions are inverses on the domain \( [-1, 1] \).

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Inverse Sine Function (sin⁻¹ or arcsin)

The inverse sine function, denoted sin⁻¹ or arcsin, returns the angle whose sine is a given value. It is defined for inputs between -1 and 1 and outputs angles in the range [-π/2, π/2]. Understanding this helps in interpreting expressions like sin(sin⁻¹ x).
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Composition of Sine and Inverse Sine Functions

When sine and its inverse are composed as sin(sin⁻¹ x), the result simplifies to x for all x in the domain [-1, 1]. This property is crucial for evaluating expressions without a calculator, as it allows direct simplification.
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Domain and Range Restrictions

The domain of sin⁻¹ is [-1, 1], and its range is limited to angles between -π/2 and π/2. Recognizing these restrictions ensures the expression is valid and helps avoid errors when simplifying or evaluating trigonometric expressions.
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Percorso guidato
4:22
Domain and Range of Function Transformations