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Ch. 2 - Graphs of the Trigonometric Functions; Inverse Trigonometric Functions
Blitzer - Trigonometry 3rd Edition
Blitzer3rd EditionTrigonometryISBN: 9780137316601Not the one you use?Change textbook
Chapter 2, Problem 1

Determine the amplitude of each function. Then graph the function and y = sin x in the same rectangular coordinate system for 0 ≤ x ≤ 2π. y = 4 sin x

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1
Identify the general form of the sine function, which is \(y = A \sin x\), where \(A\) represents the amplitude.
Recall that the amplitude of a sine function is the absolute value of the coefficient in front of \(\sin x\), so amplitude \(= |A|\).
In the given function \(y = 4 \sin x\), the coefficient \(A\) is 4, so the amplitude is \(|4|\).
To graph the function \(y = 4 \sin x\) along with \(y = \sin x\) on the same coordinate system for \(0 \leq x \leq 2\pi\), plot points for both functions at key values of \(x\) such as \(0\), \(\frac{\pi}{2}\), \(\pi\), \(\frac{3\pi}{2}\), and \(2\pi\).
Note that \(y = 4 \sin x\) will have peaks at \(4\) and troughs at \(-4\), while \(y = \sin x\) has peaks at \(1\) and troughs at \(-1\), so the graph of \(y = 4 \sin x\) is a vertically stretched version of \(y = \sin x\) by a factor of 4.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Amplitude of a Sine Function

The amplitude of a sine function y = a sin x is the absolute value of the coefficient a. It represents the maximum vertical distance from the midline (usually the x-axis) to the peak of the wave. For y = 4 sin x, the amplitude is 4, meaning the graph oscillates between -4 and 4.
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Amplitude and Reflection of Sine and Cosine

Graphing Sine Functions

Graphing a sine function involves plotting points based on its amplitude, period, and phase shift. The basic sine curve y = sin x oscillates between -1 and 1 with a period of 2π. For y = 4 sin x, the shape is similar but scaled vertically by a factor of 4, stretching the wave.
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Graph of Sine and Cosine Function

Comparing Functions on the Same Coordinate System

Plotting y = 4 sin x and y = sin x together helps visualize differences in amplitude. Both share the same period and phase but differ in vertical stretch. This comparison highlights how amplitude affects the height of the sine wave without changing its frequency or phase.
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Determining Different Coordinates for the Same Point