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Ch. 4 - Graphs of the Circular Functions
Chapter 5, Problem 4.16

For each function, give the amplitude, period, vertical translation, and phase shift, as applicable.
y = cot (x/2 + 3π/4)

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1
Identify the standard form of the cotangent function: \( y = a \cdot \cot(bx + c) + d \).
Determine the amplitude: For cotangent functions, amplitude is not defined as they do not have maximum or minimum values.
Find the period: The period of \( \cot(bx + c) \) is \( \frac{\pi}{b} \). Here, \( b = \frac{1}{2} \), so the period is \( 2\pi \).
Determine the phase shift: The phase shift is given by \( -\frac{c}{b} \). Here, \( c = \frac{3\pi}{4} \) and \( b = \frac{1}{2} \), so the phase shift is \( -\frac{3\pi}{4} \times 2 = -\frac{3\pi}{2} \).
Identify the vertical translation: The vertical translation is given by \( d \). In this function, \( d = 0 \), so there is no vertical translation.

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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. In trigonometric functions like sine and cosine, amplitude is a key feature, but for functions like cotangent, which do not oscillate above and below a central line, amplitude is not defined. Understanding amplitude is crucial for analyzing periodic functions.
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Period

The period of a trigonometric function is the length of one complete cycle of the wave. For the cotangent function, the standard period is π, but it can be altered by a coefficient in front of the variable. In the given function y = cot(x/2 + 3π/4), the period is determined by the coefficient of x, which in this case is 1/2, resulting in a period of 2π.
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Phase Shift

Phase shift refers to the horizontal displacement of a periodic function along the x-axis. It is determined by the constant added or subtracted from the variable inside the function. In the function y = cot(x/2 + 3π/4), the phase shift can be calculated by setting the inside of the cotangent function equal to zero, leading to a shift of -3π/4 to the left, which affects the function's starting point.
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