Math Problem Statement

The graph of yequals6 plus 3 cosine left parenthesis x plus StartFraction pi Over 4 EndFraction right parenthesis is obtained by shifting the graph of yequalscosine x    enter your response here ​unit(s) horizontally to the ▼ right, left, stretching it vertically by a factor of    enter your response here​, and then shifting it    enter your response here ​unit(s) vertically ▼

Solution

To analyze the transformations that turn the graph of y=cos(x)y = \cos(x) into the graph of y=6+3cos(x+π4)y = 6 + 3 \cos\left(x + \frac{\pi}{4}\right), let's break down the changes:

  1. Horizontal Shift: The expression inside the cosine, x+π4x + \frac{\pi}{4}, represents a horizontal shift. Since the +π4+\frac{\pi}{4} is added to xx, this indicates a shift to the left by π4\frac{\pi}{4} units.
    So, the graph is shifted to the left by π4\frac{\pi}{4} units.

  2. Vertical Stretch and Reflection: The coefficient 33 in front of the cosine function represents a vertical stretch by a factor of 3. The graph is stretched by 3 times the usual amplitude of the cosine function.
    There is no reflection because the coefficient is positive.

  3. Vertical Shift: The constant 66 outside the cosine function represents a vertical shift. Since it is added to the entire function, it shifts the graph up by 6 units.
    So, the graph is shifted up by 6 units.

Summary:

  • The graph of y=6+3cos(x+π4)y = 6 + 3 \cos\left(x + \frac{\pi}{4}\right) is obtained by:
    1. Shifting the graph of y=cos(x)y = \cos(x) left by π4\frac{\pi}{4} units.
    2. Stretching it vertically by a factor of 3.
    3. Shifting it up by 6 units.

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Here are some related questions:

  1. What is the effect of a negative sign in front of the cosine function?
  2. How does the period of the cosine function change if the equation is y=3cos(2x)y = 3 \cos(2x)?
  3. What happens if you shift the graph of y=cos(x)y = \cos(x) by a fraction of π\pi units?
  4. How does the phase shift affect the graph of the sine function?
  5. What is the general form of a sinusoidal function, and how do you interpret each parameter?

Tip: When analyzing transformations of sinusoidal functions like cosine or sine, remember that:

  • A positive inside shift (e.g., x+cx + c) shifts the graph to the left.
  • A negative inside shift (e.g., xcx - c) shifts the graph to the right.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Graph Transformations
Cosine Function
Amplitude
Phase Shift

Formulas

y = A cos(Bx + C) + D

Theorems

Transformation of sinusoidal functions

Suitable Grade Level

Grades 9-11