In Exercises 27–32, select the representations that do not change the location of the given point. (4, 120°) (−4, 300°)
Table of contents
- 0. Review of College Algebra4h 43m
- 1. Measuring Angles40m
- 2. Trigonometric Functions on Right Triangles2h 5m
- 3. Unit Circle1h 19m
- 4. Graphing Trigonometric Functions1h 19m
- 5. Inverse Trigonometric Functions and Basic Trigonometric Equations1h 41m
- 6. Trigonometric Identities and More Equations2h 34m
- 7. Non-Right Triangles1h 38m
- 8. Vectors2h 25m
- 9. Polar Equations2h 5m
- 10. Parametric Equations1h 6m
- 11. Graphing Complex Numbers1h 7m
- OLD 1. Angles and the Trigonometric Functions Coming soon
- OLD 2. Trigonometric Functions graphs, Inverse Trigonometric Functions Coming soon
- OLD 3. Trigonometric Identities and Equations Coming soon
- OLD 4. Laws of Sines, Cosines and Vectors Coming soon
- OLD 5. Complex Numbers, Polar Coordinates and Parametric Equations Coming soon
- NEW (not used) 7. Laws of Sines, Cosines and Vectors Coming soon
- NEW (not used) 8. Vectors Coming soon
- NEW(not used) 9. Polar equations Coming soon
- NEW (not used) 11. Graphing Complex Numbers Coming soon
9. Polar Equations
Polar Coordinate System
Problem 31
Textbook Question
In Exercises 13–34, test for symmetry and then graph each polar equation. r = 1 − 3 sin θ
Verified step by step guidance1
Recall that to test for symmetry in polar equations, we check three types: symmetry about the polar axis (x-axis), symmetry about the line \( \theta = \frac{\pi}{2} \) (y-axis), and symmetry about the pole (origin).
For symmetry about the polar axis, replace \( \theta \) with \( -\theta \) in the equation and see if the equation remains unchanged. That is, check if \( r = 1 - 3 \sin(-\theta) \) simplifies to the original equation.
For symmetry about the line \( \theta = \frac{\pi}{2} \), replace \( \theta \) with \( \pi - \theta \) and check if the equation remains unchanged. So, check if \( r = 1 - 3 \sin(\pi - \theta) \) simplifies to the original equation.
For symmetry about the pole, replace \( r \) with \( -r \) and \( \theta \) with \( \theta + \pi \), then check if the equation remains unchanged. That is, check if \( -r = 1 - 3 \sin(\theta + \pi) \) can be rearranged to the original form.
After determining the symmetries, sketch the graph by plotting points for various values of \( \theta \) between 0 and \( 2\pi \), using the equation \( r = 1 - 3 \sin \theta \), and then reflect the graph according to the symmetries found.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Polar Coordinates and Equations
Polar coordinates represent points using a radius r and an angle θ from the positive x-axis. Polar equations express r as a function of θ, describing curves in the plane. Understanding how to interpret and plot these equations is essential for graphing polar curves.
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Intro to Polar Coordinates
Symmetry Tests in Polar Graphs
Symmetry in polar graphs can be tested about the polar axis, the line θ = π/2, and the pole (origin). These tests involve substituting θ with -θ, π - θ, or replacing r with -r to check if the equation remains unchanged, helping to identify symmetrical properties of the curve.
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Cardioids
Graphing Polar Equations Involving Sine
Polar equations with sine functions, like r = 1 - 3 sin θ, often produce limaçon or cardioid shapes. Recognizing the effect of the sine term on the radius as θ varies aids in sketching the curve accurately, including identifying loops, petals, or inner loops.
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Introduction to Common Polar Equations
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Textbook Question
