Chapter 7: Problem 33
\(29-42\) . Find the amplitude, period, and phase shift of the function, and graph one complete period. $$ y=-4 \sin 2\left(x+\frac{\pi}{2}\right) $$
Short Answer
Expert verified
Amplitude: 4, Period: \(\pi\), Phase Shift: \(-\frac{\pi}{2}\) (left).
Step by step solution
01
Identify the General Form
The general form of a sine function is \( y = a \sin(bx + c) + d \). By comparing it to \( y = -4 \sin 2\left(x+\frac{\pi}{2}\right) \), we identify:- \( a = -4 \) (amplitude factor)- \( b = 2 \) (impacts period)- \( c = \pi \) (related to phase shift)- \( d = 0 \) (vertical shift)
02
Find the Amplitude
The amplitude of a sine function \( y = a \sin(bx + c) + d \) is given by the absolute value of \( a \). Therefore, the amplitude is \( |a| = |-4| = 4 \).
03
Determine the Period
The period of a sine function is calculated as \( \frac{2\pi}{b} \). For \( b = 2 \), the period becomes \( \frac{2\pi}{2} = \pi \).
04
Calculate the Phase Shift
The phase shift of a sine function is determined by \( -\frac{c}{b} \). Using \( c = \pi \) and \( b = 2 \), the phase shift is \( -\frac{\pi}{2} \). This indicates a leftward shift of \( \frac{\pi}{2} \).
05
Graph the Function
Start by sketching a standard sine wave with the given amplitude, period, and phase shift:- Amplitude: Peaks at 4 and troughs at -4.- Period: Repeats every \( \pi \) units.- Phase Shift: Start the wave \( \frac{\pi}{2} \) to the left of where it normally begins. This reflects across the x-axis due to the negative sign on \( a \) (-4). The steps are:1. Begin drawing a downward peak at \( x = -\frac{\pi}{2} \).2. Reach the maximum at \( x = 0 \) (since it's inverted).3. Complete one cycle back to \( x = \frac{\pi}{2} \).Complete the graph by continuing this pattern across one full period.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Amplitude
The amplitude of a trigonometric function, especially a sine function, concerns the height of the peaks and depth of the troughs. In simpler terms, it's about how "tall" or "deep" the wave appears on a graph.
The amplitude is found by looking at the coefficient in front of the sine function in its general form:
The amplitude is found by looking at the coefficient in front of the sine function in its general form:
- General Form: \( y = a \sin(bx + c) + d \)
- Amplitude: \(|a|\)
Period
The period of a sine function defines the length of one complete cycle of the wave. It's the horizontal distance required for the function to start repeating itself over the x-axis.
This distance is derived from the coefficient \( b \) in the general sine function formula. Here's how it works:
This distance is derived from the coefficient \( b \) in the general sine function formula. Here's how it works:
- General Form: \( y = a \sin(bx + c) + d \)
- Period Formula: \( \frac{2\pi}{b} \)
Phase Shift
Phase shift is all about the horizontal movement of a wave along the x-axis. It describes how much the entire graph shifts to the left or right, changing the starting point of the wave.
The phase shift is calculated using the constants \( c \) and \( b \):
The phase shift is calculated using the constants \( c \) and \( b \):
- Formula: \( -\frac{c}{b} \)
Sine Function
Sine functions are fundamental trigonometric functions that model periodic phenomena. They have a characteristic "wave-like" pattern that makes them useful for describing cyclic behaviors, such as sound waves or tidal patterns.
The standard sine function is defined mathematically as:
The standard sine function is defined mathematically as:
- General Formula: \( y = a \sin(bx + c) + d \)
- Key Components: Amplitude \(a\), Frequency \(b\), Phase Shift derived from \(c\), and Vertical Shift \(d\)
- The negative sign before \( 4 \) indicates the wave is reflected over the x-axis.
- The function repeats itself every \( \pi \) units with an amplitude of 4.
- With a phase shift of \( -\frac{\pi}{2} \), the wave's starting point is moved left compared to the typical sine wave.