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Ch. 4 - Graphs of the Circular Functions
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161, 9780135440780, 9780136881117, 9780135440827, 9780135924891Non è quello che usi tu?Cambia libro di testo
Capitolo 5, Problema 14

For each function, give the amplitude, period, vertical translation, and phase shift, as applicable.
y = 2 sec(πx - 2π)

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Identify the general form of the secant function: \(y = a \sec(bx - c) + d\), where \(a\) is the amplitude factor, \(b\) affects the period, \(c\) relates to the phase shift, and \(d\) is the vertical translation.
Determine the amplitude: For secant functions, amplitude is not typically defined because secant can take on values from \(-\infty\) to \(-1\) and from \(1\) to \(\infty\). However, the coefficient \(a\) affects the vertical stretch or compression. Here, \(a = 2\).
Calculate the period using the formula \(\text{Period} = \frac{2\pi}{|b|}\). From the function, \(b\) is the coefficient of \(x\) inside the argument of secant. Identify \(b\) from \(\pi x\) as \(b = \pi\).
Find the phase shift using the formula \(\text{Phase shift} = \frac{c}{b}\), where \(c\) is the constant subtracted inside the argument. Here, \(c = 2\pi\), so calculate the phase shift accordingly.
Determine the vertical translation \(d\). Since there is no constant added or subtracted outside the secant function, \(d = 0\), meaning no vertical shift.

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Amplitude of Trigonometric Functions

Amplitude measures the maximum distance a function's value deviates from its midline. For secant functions, which are reciprocals of cosine, amplitude is not defined because secant values can grow without bound. Instead, focus on transformations affecting the graph's shape and position.
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Introduction to Trigonometric Functions

Period of Secant Function

The period of a secant function is derived from its related cosine function. The standard period of sec(x) is 2π, but when the function is sec(bx), the period becomes 2π divided by |b|. This determines the length of one complete cycle of the function.
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Graphs of Secant and Cosecant Functions

Phase Shift and Vertical Translation

Phase shift refers to the horizontal shift of the function's graph, calculated by setting the inside of the function's argument equal to zero and solving for x. Vertical translation shifts the graph up or down by adding or subtracting a constant outside the function. In y = 2 sec(πx - 2π), phase shift is found by solving πx - 2π = 0, and there is no vertical translation since no constant is added.
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