Chapter 4: Problem 46
Graph one complete cycle for each of the following. In each case, label the axes so that the amplitude and period are easy to read. $$ y=2 \sin 4 x $$
Short Answer
Expert verified
Amplitude is 2, period is \( \frac{\pi}{2} \). Label axes accordingly and plot critical points.
Step by step solution
01
Identify Amplitude and Period
The function given is \( y = 2 \sin 4x \). The amplitude is the coefficient of the sine function, which is 2. The period of a sine function is given by \( \frac{2\pi}{|b|} \), where \( b \) is the coefficient of \( x \). In this case, \( b = 4 \), so the period is \( \frac{2\pi}{4} = \frac{\pi}{2} \).
02
Set Up the Axes
Label the vertical axis with multiples of the amplitude. Since the amplitude is 2, the vertical axis should be labeled from -2 to 2. For the horizontal axis, since the period is \( \frac{\pi}{2} \), label it such that one complete cycle fits within this interval. This means marking the horizontal axis with divisions at \( 0, \frac{\pi}{8}, \frac{\pi}{4}, \frac{3\pi}{8}, \) and \( \frac{\pi}{2} \).
03
Plot Critical Points and Sketch the Graph
At \( x = 0 \), \( \sin(0) = 0 \), so \( y = 0 \). At \( x = \frac{\pi}{8} \), \( \sin\left(4 \times \frac{\pi}{8}\right) = \sin\left(\frac{\pi}{2}\right) = 1 \), so \( y = 2 \). At \( x = \frac{\pi}{4} \), \( \sin\left(4 \times \frac{\pi}{4}\right) = \sin(\pi) = 0 \), so \( y = 0 \). At \( x = \frac{3\pi}{8} \), \( \sin\left(4 \times \frac{3\pi}{8}\right) = \sin\left(\frac{3\pi}{2}\right) = -1 \), so \( y = -2 \). At \( x = \frac{\pi}{2} \), \( \sin(2\pi) = 0 \), so \( y = 0 \). Plot these points and sketch the sine curve connecting them smoothly.
04
Finalize the Graph
Ensure the graph shows one complete cycle from \( x = 0 \) to \( x = \frac{\pi}{2} \). The vertical axis should range from -2 to 2, showing the maximum and minimum values of the sine function. The horizontal axis confirms that the period is \( \frac{\pi}{2} \), illustrating one full cycle of the function.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Graphing Trigonometric Functions
Graphing trigonometric functions like the sine or cosine can provide a visual representation of their cyclical nature.
These graphs are periodic and repeat after a specific interval, known as the period. When graphing, it's important to capture one complete cycle to show this pattern clearly.
When graphing the function \( y = 2 \sin 4x \):
These graphs are periodic and repeat after a specific interval, known as the period. When graphing, it's important to capture one complete cycle to show this pattern clearly.
When graphing the function \( y = 2 \sin 4x \):
- The first step is to identify key parameters like amplitude and period.
- Next, set up your axes based on these parameters for better visibility.
- Mark and plot critical points within the determined interval.
- Draw a smooth curve through these points to complete the graph.
Amplitude of Sine Function
Amplitude is a critical feature of trigonometric functions that dictates their vertical stretch. It tells us how far the graph stretches from its midline.
For a sine function \( y = a \sin bx \), the amplitude is the absolute value of \( a \).
In our exercise with \( y = 2 \sin 4x \):
For a sine function \( y = a \sin bx \), the amplitude is the absolute value of \( a \).
In our exercise with \( y = 2 \sin 4x \):
- The amplitude is 2, meaning the wave reaches a maximum and minimum of 2 and -2, respectively.
- The vertical axis should be marked from -2 to 2 to reflect these values.
- This clearly shows the function oscillating between its maximum and minimum values.
Period of Trigonometric Functions
The period of a trigonometric function indicates the interval after which the function repeats its pattern.
For functions of the form \( y = a \sin bx \), the period is calculated using \( \frac{2\pi}{|b|} \).
In our equation \( y = 2 \sin 4x \):
For functions of the form \( y = a \sin bx \), the period is calculated using \( \frac{2\pi}{|b|} \).
In our equation \( y = 2 \sin 4x \):
- The coefficient \( b = 4 \), so the period is \( \frac{2\pi}{4} = \frac{\pi}{2} \).
- This tells us that a complete cycle of the sine function occurs between \( x = 0 \) and \( x = \frac{\pi}{2} \).
- Mark and divide the horizontal axis accordingly to fit one cycle within this range.