Chapter 6: Problem 13
For each of the following equations, find the amplitude, period, horizontal shift, and midline. \(y=2 \sin (3 x-21)+4\)
Short Answer
Expert verified
Amplitude: 2, Period: \(\frac{2\pi}{3}\), Horizontal Shift: 7 units, Midline: \(y=4\).
Step by step solution
01
Identify the Standard Form
The standard form for a sine function is \( y = a \sin(bx - c) + d \). Comparing this with \( y = 2 \sin(3x - 21) + 4 \), we identify \( a = 2 \), \( b = 3 \), \( c = 21 \), and \( d = 4 \).
02
Calculate the Amplitude
The amplitude of a sine function is given by the absolute value of \( a \). Here, \( a = 2 \), so the amplitude is \( |2| = 2 \).
03
Determine the Period
The period of a sine function is calculated using the formula \( \frac{2\pi}{b} \). With \( b = 3 \), the period is \( \frac{2\pi}{3} \).
04
Calculate the Horizontal Shift
The horizontal shift, also called phase shift, is given by \( \frac{c}{b} \). Here, \( c = 21 \) and \( b = 3 \), so the horizontal shift is \( \frac{21}{3} = 7 \). This means the graph shifts 7 units to the right.
05
Identify the Midline
The midline of a sine function is given by \( y = d \). Here, \( d = 4 \), so the midline is \( y = 4 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Sine Function
In trigonometry, the sine function is a fundamental element with distinct features like amplitude, period, and more. It is generally represented in the format:
- Equation Form: \( y = a \sin(bx - c) + d \)
- Function Behavior: Repetitive oscillations that look like waves on a graph.
- Key Parameters: \( a \) (Amplitude), \( b \) (Frequency), \( c \) (Phase Shift), \( d \) (Vertical Shift)
Amplitude
Amplitude in a sine function can be thought of as the height of the wave from the midline to the peak. It's the measure of the extent of the wave's oscillation.
- Calculation: Amplitude is given by the value |\( a \)| where \( a \) is the coefficient in the equation of the sine function.
- In the standard form equation \( y = a \sin(bx - c) + d \), the amplitude is determined by \( a \).
- Example from Exercise: In \( y = 2 \sin(3x - 21) + 4 \), \( a = 2 \), so the amplitude is 2.
Period
The period of a sine function refers to how long it takes for the function to complete one full cycle of its wave. The period can be influenced by the frequency of the function,
- Formula: The period is calculated as \( \frac{2\pi}{b} \), where \( b \) is the frequency component in the sine function’s equation.
- In the equation \( y = 2 \sin(3x - 21) + 4 \), the period is determined using \( b = 3 \). Therefore the period is \( \frac{2\pi}{3} \).
- Interpretation: A smaller period means the waves repeat more frequently within a shorter amount of time.
Phase Shift
Phase shift in the sine function relates to a horizontal translation of the graph left or right along the x-axis. This is key in determining where the wave cycle starts along the x-axis.
- Calculation: Phase shift is obtained by \( \frac{c}{b} \), where \( c \) and \( b \) originate from the transformed sine function equation.
- From the equation \( y = 2 \sin(3x - 21) + 4 \), \( c = 21 \) and \( b = 3 \), making the phase shift \( \frac{21}{3} = 7 \).
- Direction: A positive phase shift indicates the graph shifts to the right, while a negative shift moves it to the left.