Without calculating derivatives, determine the slopes of each of the lines tangent to the curve r=8 cos θ−4 at the origin.
Table of contents
- 0. Functions7h 54m
- Introduction to Functions16m
- Piecewise Functions10m
- Properties of Functions9m
- Common Functions1h 8m
- Transformations5m
- Combining Functions27m
- Exponent rules32m
- Exponential Functions28m
- Logarithmic Functions24m
- Properties of Logarithms36m
- Exponential & Logarithmic Equations35m
- Introduction to Trigonometric Functions38m
- Graphs of Trigonometric Functions44m
- Trigonometric Identities47m
- Inverse Trigonometric Functions48m
- 1. Limits and Continuity2h 2m
- 2. Intro to Derivatives1h 33m
- 3. Techniques of Differentiation3h 18m
- 4. Applications of Derivatives2h 38m
- 5. Graphical Applications of Derivatives6h 2m
- 6. Derivatives of Inverse, Exponential, & Logarithmic Functions2h 37m
- 7. Antiderivatives & Indefinite Integrals1h 26m
- 8. Definite Integrals4h 44m
- 9. Graphical Applications of Integrals2h 27m
- 10. Physics Applications of Integrals 3h 16m
- 11. Integrals of Inverse, Exponential, & Logarithmic Functions2h 34m
- 12. Techniques of Integration7h 41m
- 13. Intro to Differential Equations2h 55m
- 14. Sequences & Series5h 36m
- 15. Power Series2h 19m
- 16. Parametric Equations & Polar Coordinates7h 58m
16. Parametric Equations & Polar Coordinates
Polar Coordinates
Problem 12.2.43
Textbook Question
37–48. Polar-to-Cartesian coordinates Convert the following equations to Cartesian coordinates. Describe the resulting curve.
r = 6 cos θ + 8 sin θ
Verified step by step guidance1
Recall the relationships between polar and Cartesian coordinates: \(x = r \cos \theta\) and \(y = r \sin \theta\). Also, \(r^2 = x^2 + y^2\).
Start with the given polar equation: \(r = 6 \cos \theta + 8 \sin \theta\).
Multiply both sides of the equation by \(r\) to eliminate the denominator when substituting: \(r \cdot r = r (6 \cos \theta + 8 \sin \theta)\), which gives \(r^2 = 6r \cos \theta + 8r \sin \theta\).
Substitute \(r^2\) with \(x^2 + y^2\), \(r \cos \theta\) with \(x\), and \(r \sin \theta\) with \(y\) to get: \(x^2 + y^2 = 6x + 8y\).
Rewrite the equation to standard form by bringing all terms to one side: \(x^2 - 6x + y^2 - 8y = 0\). Then, complete the square for both \(x\) and \(y\) terms to identify the type and properties of the curve.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Polar and Cartesian Coordinate Systems
Polar coordinates represent points using a radius and an angle (r, θ), while Cartesian coordinates use (x, y) positions on a plane. Understanding how to convert between these systems is essential for analyzing curves defined in polar form.
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Conversion Formulas Between Polar and Cartesian Coordinates
The key formulas for conversion are x = r cos θ and y = r sin θ. Additionally, r² = x² + y² and tan θ = y/x. These relationships allow rewriting polar equations in terms of x and y to identify the curve in Cartesian form.
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Intro to Polar Coordinates
Identifying and Describing Curves from Equations
After converting to Cartesian form, recognizing the type of curve (e.g., circle, ellipse, line) involves rearranging the equation and comparing it to standard forms. This helps in describing the geometric shape represented by the original polar equation.
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