Math Problem Statement

Graph y = -2 - cos(3θ). First choose the appropriate starting graph, then transform it to make the graph of y = -2 - cos(3θ).

Solution

The task here involves graphing the function y=2cos(3θ)y = -2 - \cos(3\theta). Let's break this down step by step:

Step 1: Recognize the base graph

  • The base function is cos(3θ)\cos(3\theta), which is a cosine graph with a frequency multiplier of 3, meaning the cosine wave completes 3 cycles over 2π2\pi. This makes the period 2π3\frac{2\pi}{3}.
  • From the image of the starting graphs, the one that represents the cosine graph should be chosen as the base. The cosine graph typically starts at its maximum value, reaches a minimum, and returns to the maximum, resembling a wave pattern.

Step 2: Apply transformations

Now, we need to apply two transformations to this base cosine function:

  1. Vertical Stretch:

    • The factor of 1-1 in front of the cosine function reflects the graph across the horizontal axis. So, instead of starting at a maximum, the graph will start at a minimum.
  2. Vertical Shift:

    • The term 2-2 shifts the entire graph downward by 2 units.

Final Function: y=2cos(3θ)y = -2 - \cos(3\theta)

  • This means the graph starts at y=3y = -3 (minimum), oscillates between y=3y = -3 and y=1y = -1, and has a period of 2π3\frac{2\pi}{3}.

To summarize:

  • Choose the cosine graph from the options (likely the second or third from the left).
  • Transform it by reflecting it over the x-axis and shifting it downward by 2 units.

Would you like more details on this process? Here are five related questions to deepen understanding:

  1. How does the frequency factor 3θ3 \theta affect the graph's period?
  2. What are the amplitude and range of the transformed graph?
  3. What effect does the negative sign in front of the cosine function have?
  4. How would the graph change if the transformation included a horizontal shift?
  5. How can you determine the key points on the graph of y=2cos(3θ)y = -2 - \cos(3\theta)?

Tip: Always analyze the effect of both vertical and horizontal transformations separately before combining them.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Trigonometry
Graph Transformations
Cosine Function

Formulas

y = A + Bcos(Cθ)
Period of cosine function: 2π/C
Amplitude and vertical shift

Theorems

Cosine Graph Period and Amplitude

Suitable Grade Level

Grades 10-12