Math Problem Statement

Find the range of f(x) = 1 + 2|cos(πx) + 1/2| algebraically. Graph the function f(x) = 1 + 2|cos(πx) + 1/2|.

Solution

Let's break down and solve both parts (a) and (b) of this problem step by step.

(a) Find the range of f(x)=1+2cos(πx)+12f(x) = 1 + 2|\cos(\pi x) + \frac{1}{2}|, algebraically.

Step 1: Start with the range of cosx\cos x

We know that the cosine function, cosx\cos x, has a range of [1,1][-1, 1].

Step 2: Analyze cos(πx)\cos(\pi x)

Since cos(πx)\cos(\pi x) is simply a horizontal stretch of cosx\cos x, its range will also be [1,1][-1, 1]. This is because multiplying the input of the cosine function by π\pi does not affect its range.

Step 3: Apply the transformation cos(πx)+12\cos(\pi x) + \frac{1}{2}

The next step is to add 12\frac{1}{2} to cos(πx)\cos(\pi x). When you add 12\frac{1}{2} to any value in [1,1][-1, 1], the new range becomes: [ \left[ -1 + \frac{1}{2}, 1 + \frac{1}{2} \right] = \left[ -\frac{1}{2}, \frac{3}{2} \right] ]

Step 4: Take the absolute value cos(πx)+12|\cos(\pi x) + \frac{1}{2}|

The absolute value operation affects negative values by making them positive. Thus, the range of cos(πx)+12|\cos(\pi x) + \frac{1}{2}| becomes: [0,32]\left[ 0, \frac{3}{2} \right] because the smallest value 12-\frac{1}{2} is turned into 0.

Step 5: Multiply by 2

Now, multiplying by 2 stretches the range. So, we multiply each value in the range [0,32][0, \frac{3}{2}] by 2: [0,3]\left[ 0, 3 \right]

Step 6: Add 1

Finally, adding 1 shifts the entire range upward by 1, so the final range of f(x)f(x) becomes: [1,4]\left[ 1, 4 \right]

Thus, the range of f(x)=1+2cos(πx)+12f(x) = 1 + 2|\cos(\pi x) + \frac{1}{2}| is [1,4][1, 4].

(b) Graph the function f(x)=1+2cos(πx)+12f(x) = 1 + 2|\cos(\pi x) + \frac{1}{2}|

You are asked to graph this function by starting with the graph of y=cosxy = \cos x and applying appropriate transformations step by step. Let's outline the transformations:

  1. Start with the base graph y=cosxy = \cos x:

    • The cosine graph oscillates between 1-1 and 11.
  2. Apply horizontal scaling to get cos(πx)\cos(\pi x):

    • This stretches the cosine function horizontally by a factor of π\pi.
  3. Shift vertically by +12+\frac{1}{2} to get cos(πx)+12\cos(\pi x) + \frac{1}{2}:

    • This shifts the graph upward by 0.5 units, so it now oscillates between 12-\frac{1}{2} and 32\frac{3}{2}.
  4. Apply absolute value to get cos(πx)+12|\cos(\pi x) + \frac{1}{2}|:

    • Any negative parts of the graph (those that dipped below 0) are reflected above the x-axis.
  5. Multiply by 2 to get 2cos(πx)+122|\cos(\pi x) + \frac{1}{2}|:

    • This stretches the graph vertically, so it now oscillates between 0 and 3.
  6. Add 1 to get 1+2cos(πx)+121 + 2|\cos(\pi x) + \frac{1}{2}|:

    • Finally, shift the entire graph upward by 1 unit, resulting in the final range from 1 to 4.

These transformations would produce the graph step-by-step. You are asked to draw and annotate each transformation, resulting in six graphs, including the original y=cosxy = \cos x.


Do you want a detailed drawing of each transformation?

Here are five related questions for you:

  1. How does the period of cos(πx)\cos(\pi x) compare to cos(x)\cos(x)?
  2. What effect does taking the absolute value of a function have on its graph?
  3. Why does multiplying by 2 stretch the graph vertically?
  4. How do you determine the amplitude of a cosine function after transformations?
  5. What happens to the graph of cos(x)\cos(x) when you shift it vertically by a constant?

Tip: When graphing functions, always apply transformations step by step in the correct order to avoid mistakes!

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Trigonometry
Cosine function transformations
Absolute value functions
Range of functions
Graph transformations

Formulas

cos(x) has a range of [-1, 1]
Absolute value transformation |x|
Range of f(x) = a|cos(πx) + b| + c

Theorems

Range of cosine function
Graph transformation rules (vertical shifts, stretching, and absolute value operations)

Suitable Grade Level

Grades 10-12