Chapter 1: Problem 31
\(23-36\) . Graph the function by hand, not by plotting points, but by starting with the graph of one of the standard functions and then applying the appropriate transformations. $$y=\frac{1}{2}(1-\cos x)$$
Short Answer
Expert verified
Start with \( \cos x \), reflect, shift up, and compress vertically.
Step by step solution
01
Identify the Standard Function
The given function is \( y = \frac{1}{2}(1 - \cos x) \). Recognize that the standard function here is \( \cos x \).
02
Transform the Standard Function
The transformation involved is modifying \( \cos x \) with \( 1 - \cos x \). This shifts the cosine graph upwards by 1 unit and reflects it across the x-axis.
03
Apply Vertical Compression
The factor \( \frac{1}{2} \) in \( \frac{1}{2}(1 - \cos x) \) compresses the graph vertically. This reduces the amplitude, making the range [0, 1].
04
Combine Transformations
Combine the transformations: the original \( \cos x \) graph is reflected over the x-axis, shifted up by 1, and then compressed vertically by factor of \( \frac{1}{2} \). The maximum value becomes 1 and the minimum becomes 0.
05
Final Graph
Begin with \( y = \cos x \), apply the transformations to follow the behavior of \( y = \frac{1}{2}(1 - \cos x) \). Sketch the curve from \( x = 0 \), passing through turning points at \((\pi, 0)\), \((2\pi, 1)\), forming a wave-like shape that repeats every \(2\pi\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Trigonometric Functions
Trigonometric functions play a crucial role in mathematics, especially when it comes to modeling periodic phenomena. The primary trigonometric functions include sine (\( \sin x \) ), cosine (\( \cos x \) ), and tangent (\( \tan x \) ). These functions have specific patterns or waves, which makes them ideal for representing cyclical behaviors such as sound waves or circadian rhythms.
- Sine and cosine functions are periodic with a period of \(2\pi\).
- The amplitude is the height from the center line to the peak.
- Cosine starts at its maximum value when \( x = 0 \), while sine starts at zero.
Cosine Transformation
Transformations of the cosine function involve altering its basic shape or position. In the case of the function \( y = \frac{1}{2}(1 - \cos x) \), we are making adjustments on two fronts. First, consider the transformation inside the brackets: \(1 - \cos x\). This shifts the graph up by 1 unit and effectively flips it around the x-axis. Originally, \(\cos x\) starts at its peak, but \(1 - \cos x\) starts at its lowest.By shifting and reflecting,
- The peak of the cosine, usually at 1, starts now at 0.
- The typical increase from 0 up to 1 becomes a decrease from 1 to 0.
Vertical Compression
Vertical compression changes the height of a wave graph without altering its horizontal dimensions. In the equation \( y = \frac{1}{2}(1 - \cos x) \), \(\frac{1}{2}\) compresses the graph vertically, reducing the amplitude. This means the wave does not reach as high or dip as low as the original cosine wave.
- The standard \( \cos x \) function has an amplitude of 1.
- When compressed by a factor of \( \frac{1}{2} \), its maximum and minimum values become 0.5 and 0.
- This makes the range from [0, 1] in the final form after other transformations have been applied.
Reflection Over X-axis
A reflection of a function across the x-axis involves flipping the graph upside down. This transformation dramatically impacts how the graph behaves visually. In our case with \( y = \frac{1}{2}(1 - \cos x) \), the reflection is due to subtracting the cosine part from 1.
- Typical peaks of cosine graphs get inverted.
- When think of reflection, consider it as turning the peaks into troughs and vice versa.