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Ch. 4 - Graphs of the Circular Functions
Chapter 5, Problem 4.12

For each function, give the amplitude, period, vertical translation, and phase shift, as applicable.
y = -sin (x - 3π/4)

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1
Identify the standard form of the sine function: \( y = a \sin(b(x - c)) + d \).
Compare the given function \( y = -\sin(x - \frac{3\pi}{4}) \) with the standard form to identify parameters: \( a = -1 \), \( b = 1 \), \( c = \frac{3\pi}{4} \), and \( d = 0 \).
Determine the amplitude: The amplitude is the absolute value of \( a \), which is \( |a| = |-1| = 1 \).
Calculate the period: The period of a sine function is given by \( \frac{2\pi}{b} \). Since \( b = 1 \), the period is \( \frac{2\pi}{1} = 2\pi \).
Identify the phase shift and vertical translation: The phase shift is \( c = \frac{3\pi}{4} \) to the right, and the vertical translation is \( d = 0 \), meaning there is no vertical shift.

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Key Concepts

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

Amplitude

Amplitude refers to the maximum distance a wave reaches from its central axis or equilibrium position. For sine and cosine functions, it is determined by the coefficient in front of the function. In the case of y = -sin(x - 3π/4), the amplitude is 1, as the coefficient is -1, indicating the wave will oscillate between 1 and -1.
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Period

The period of a trigonometric function is the length of one complete cycle of the wave. For the sine function, the standard period is 2π. In the equation y = -sin(x - 3π/4), there is no coefficient affecting the x variable, so the period remains 2π, meaning the function will repeat every 2π units along the x-axis.
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Phase Shift

Phase shift refers to the horizontal displacement of a periodic function from its standard position. It is determined by the value subtracted from x in the function. In y = -sin(x - 3π/4), the phase shift is 3π/4 to the right, indicating that the entire sine wave is shifted 3π/4 units along the x-axis.
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