Math Problem Statement

Consider the polar equation r = 2 - 2cos(θ). Complete the table of values for r = 2 - 2cos(θ) at specific angles and sketch the graph using the calculated points.

Solution

To solve this question, let’s first address Part (a) and complete the table for the polar equation r=22cos(θ)r = 2 - 2\cos(\theta). For each given value of θ\theta, substitute it into the equation to find the corresponding rr.

1. Completing the Table

The polar equation is: r=22cos(θ)r = 2 - 2\cos(\theta)

We evaluate rr at the given values of θ\theta:

  1. For θ=0\theta = 0: r=22cos(0)=22(1)=0r = 2 - 2\cos(0) = 2 - 2(1) = 0

  2. For θ=π3\theta = \frac{\pi}{3}: r=22cos(π3)=22(12)=21=1r = 2 - 2\cos\left(\frac{\pi}{3}\right) = 2 - 2\left(\frac{1}{2}\right) = 2 - 1 = 1

  3. For θ=π2\theta = \frac{\pi}{2}: r=22cos(π2)=22(0)=2r = 2 - 2\cos\left(\frac{\pi}{2}\right) = 2 - 2(0) = 2

  4. For θ=2π3\theta = \frac{2\pi}{3}: r=22cos(2π3)=22(12)=2+1=3r = 2 - 2\cos\left(\frac{2\pi}{3}\right) = 2 - 2\left(-\frac{1}{2}\right) = 2 + 1 = 3

  5. For θ=π\theta = \pi: r=22cos(π)=22(1)=2+2=4r = 2 - 2\cos(\pi) = 2 - 2(-1) = 2 + 2 = 4

  6. For θ=4π3\theta = \frac{4\pi}{3}: r=22cos(4π3)=22(12)=2+1=3r = 2 - 2\cos\left(\frac{4\pi}{3}\right) = 2 - 2\left(-\frac{1}{2}\right) = 2 + 1 = 3

  7. For θ=3π2\theta = \frac{3\pi}{2}: r=22cos(3π2)=22(0)=2r = 2 - 2\cos\left(\frac{3\pi}{2}\right) = 2 - 2(0) = 2

  8. For θ=5π3\theta = \frac{5\pi}{3}: r=22cos(5π3)=22(12)=21=1r = 2 - 2\cos\left(\frac{5\pi}{3}\right) = 2 - 2\left(\frac{1}{2}\right) = 2 - 1 = 1

  9. For θ=2π\theta = 2\pi: r=22cos(2π)=22(1)=0r = 2 - 2\cos(2\pi) = 2 - 2(1) = 0

The completed table is:

θ\theta00π3\frac{\pi}{3}π2\frac{\pi}{2}2π3\frac{2\pi}{3}π\pi4π3\frac{4\pi}{3}3π2\frac{3\pi}{2}5π3\frac{5\pi}{3}2π2\pi
rr001122334433221100

2. Sketching the Graph

In Part (b), use the table values to plot points in the polar graph. For each pair of (θ,r)(\theta, r):

  1. Start at the angle θ\theta and move outward along the radius by rr.
  2. Connect the points to form the graph of r=22cos(θ)r = 2 - 2\cos(\theta).

Let me know if you'd like me to help plot the graph or explain the process further!


Relative Questions:

  1. What is the significance of symmetry in polar graphs?
  2. How does the graph of r=22cos(θ)r = 2 - 2\cos(\theta) compare to a standard cardioid?
  3. What happens if the coefficient of cos(θ)\cos(\theta) changes in the equation?
  4. How would the graph look for r=2+2cos(θ)r = 2 + 2\cos(\theta)?
  5. Why does r=22cos(θ)r = 2 - 2\cos(\theta) return to r=0r = 0 at 2π2\pi?

Tip: In polar graphs, pay attention to symmetry and intercepts for faster plotting!

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Math Problem Analysis

Mathematical Concepts

Polar Coordinates
Trigonometry
Graphing Polar Equations

Formulas

r = 2 - 2cos(θ)

Theorems

Cosine Function Symmetry
Polar Graph Symmetry

Suitable Grade Level

Grades 10-12