In Exercises 35–42, determine the amplitude and period of each function. Then graph one period of the function. y = 4 cos 2πx
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Graphs of the Sine and Cosine Functions
Problem 47
Textbook Question
In Exercises 43–52, determine the amplitude, period, and phase shift of each function. Then graph one period of the function. y = 1/2 cos (3x + π/2)
Verified step by step guidance1
Identify the general form of the cosine function: \(y = A \cos(Bx + C)\), where \(A\) is the amplitude, \(B\) affects the period, and \(C\) affects the phase shift.
Find the amplitude by taking the absolute value of \(A\). In this case, \(A = \frac{1}{2}\), so the amplitude is \(|\frac{1}{2}|\).
Calculate the period using the formula \(\text{Period} = \frac{2\pi}{|B|}\). Here, \(B = 3\), so substitute to find the period.
Determine the phase shift using the formula \(\text{Phase shift} = -\frac{C}{B}\). Given \(C = \frac{\pi}{2}\) and \(B = 3\), substitute these values to find the phase shift.
To graph one period of the function, start at the phase shift on the x-axis, then plot points over one full period length, using the amplitude to determine the maximum and minimum values of the cosine wave.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Amplitude of a Trigonometric Function
Amplitude is the maximum absolute value of a trigonometric function, representing the height from the midline to the peak. For functions like y = A cos(Bx + C), the amplitude is |A|. In this example, the amplitude is 1/2, indicating the graph oscillates between 1/2 and -1/2.
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Period of a Trigonometric Function
The period is the length of one complete cycle of the function along the x-axis. For y = cos(Bx + C), the period is calculated as 2π divided by |B|. Here, B = 3, so the period is 2π/3, meaning the function repeats every 2π/3 units.
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Phase Shift of a Trigonometric Function
Phase shift refers to the horizontal translation of the graph, determined by solving Bx + C = 0 for x. It is given by -C/B. In this function, the phase shift is -π/2 divided by 3, or -π/6, indicating the graph shifts π/6 units to the left.
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