Chapter 1: Problem 62
For $$f(x)=A \sin \left(\frac{2 \pi}{B}(x-C)\right)+D$$ identify \(A, B, C,\) and \(D\) for the sine functions in Exercises \(61-64\) and sketch their graphs (see Figure \(1.76 ) .\) $$ y=\frac{1}{2} \sin (\pi x-\pi)+\frac{1}{2} $$
Short Answer
Expert verified
A = 1/2, B = 2, C = 1, D = 1/2.
Step by step solution
01
Identify the amplitude (A)
The given function is in the form: \[ y = A \sin\left(\frac{2\pi}{B}(x - C)\right) + D \] The sine function we have is: \[ y = \frac{1}{2} \sin(\pi x - \pi) + \frac{1}{2} \] In this function, \(A\) represents the amplitude of the sine wave, which is the coefficient of \(\sin\). Here, \(A = \frac{1}{2}\).
02
Determine the period factor (B)
The term \(\frac{2\pi}{B}\) inside the sine function relates to the period of the sine wave. In the function \(\sin(\pi x)\), \(\pi\) can be equated to \(\frac{2\pi}{B}\). Solving for \(B\) gives: \[ \pi = \frac{2\pi}{B} \] This implies: \[ B = 2 \]
03
Identify the phase shift (C)
The phase shift \(C\) is the horizontal shift from the origin and comes from the expression \((x - C)\). In our function, the expression inside the sine function is \(\pi x - \pi\). By factoring out \(\pi\), we have: \[ \pi(x - 1) \] Thus, \(C = 1\).
04
Find the vertical shift (D)
The vertical shift \(D\) is indicated by the constant addition outside the sine function. In \(y = \frac{1}{2} \sin(\pi x - \pi) + \frac{1}{2}\), the vertical shift \(D = \frac{1}{2}\).
05
Sketch the Graph
To sketch the graph:1. Start at the phase shift \(x = 1\) and consider the vertical shift upwards by \(\frac{1}{2}\).2. The amplitude is \(\frac{1}{2}\) and the period is determined by \(B = 2\) (one complete cycle occurs every 2 units).3. Plot key points by calculating sine values at critical points within the given period and shift.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Amplitude
When talking about sinusoidal functions, the amplitude is a measure of how high and low the wave goes. Imagine it as the wave's height.
- In a sine function like \( y = A \sin(\text{something}) + D \), \( A \) represents the amplitude.
- The amplitude is always a positive value.
- In our example function, \( y = \frac{1}{2} \sin(\pi x - \pi) + \frac{1}{2} \), the amplitude \( A \) is \( \frac{1}{2} \).
- This means the wave will reach a maximum height of \( \frac{1}{2} \) above and below the central axis of the graph, which in this case is raised by the vertical shift.
Period
The period of a sine function determines how quickly the wave completes one full cycle. It helps us understand the timing of the wave.
- In the function \( y = A \sin\left(\frac{2\pi}{B}(x - C)\right) + D \), the period is related to the value \( B \).
- Mathematically, the period \( T \) is calculated using \( T = \frac{2\pi}{B} \).
- In our specific function, \( y = \frac{1}{2} \sin(\pi x - \pi) + \frac{1}{2} \), we found that \( B = 2 \).
- Therefore, the period \( T \) is \( 2 \). This indicates the sine wave completes one full cycle every 2 units along the x-axis.
Phase Shift
The phase shift of a trigonometric function refers to the horizontal shifting along the x-axis. It's all about where the wave starts.
- For a function \( y = A \sin\left(\frac{2\pi}{B}(x - C)\right) + D \), the term \( C \) determines this shift.
- By rewriting the expression inside the sine in \( \sin(\pi x - \pi) \) as \( \pi(x - 1) \)
- We find that \( C = 1 \).
- This tells us the graph of the sine wave starts at \( x = 1 \) instead of the usual origin \( x = 0 \).
Vertical Shift
The vertical shift moves the entire sine wave up or down along the y-axis, altering its central alignment.
- In the framework \( y = A \sin\left(...\right) + D \), \( D \) accounts for the vertical shift.
- In the function\( y = \frac{1}{2} \sin(\pi x - \pi) + \frac{1}{2} \), \( D = \frac{1}{2} \).
- This shift indicates the entire sine wave is lifted upward by \( \frac{1}{2} \) unit.
- The midline, which the wave oscillates around, is now at \( y = \frac{1}{2} \) instead of the x-axis (\( y = 0 \)).