Chapter 7: Problem 282
For the following exercises, consider the following polar equations of conics. Determine the eccentricity and identify the conic. \(r=\frac{5}{-1+2 \sin \theta}\)
Short Answer
Expert verified
Eccentricity is 2; conic is a hyperbola.
Step by step solution
01
Understanding the Polar Equation
The given polar equation is \( r = \frac{5}{-1 + 2 \sin \theta} \). This equation is in the form \( r = \frac{ed}{1 - e \sin \theta} \) for conics where the directrix is vertical with \( \theta = 90^\circ \). Our job is to identify the eccentricity \( e \) and determine the type of conic it represents.
02
Comparing with the Standard Form
To find the eccentricity, compare \( r = \frac{5}{-1 + 2 \sin \theta} \) with \( r = \frac{ed}{1 - e \sin \theta} \). Here, \( e = 2 \) and \( ed = 5 \), so \( d \) can be calculated as \( d = \frac{5}{2} \).
03
Determine the Eccentricity
From the comparison, we find that the eccentricity \( e \) is 2. The eccentricity is a key feature in determining the type of conic.
04
Identifying the Conic Type
Based on conic properties: - If \( e = 1 \), it's a parabola.- If \( e < 1 \), it's an ellipse.- If \( e > 1 \), it's a hyperbola.Since \( e = 2 > 1 \), the conic is identified as a hyperbola.
Unlock Step-by-Step Solutions & Ace Your Exams!
-
Full Textbook Solutions
Get detailed explanations and key concepts
-
Unlimited Al creation
Al flashcards, explanations, exams and more...
-
Ads-free access
To over 500 millions flashcards
-
Money-back guarantee
We refund you if you fail your exam.
Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!
Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Eccentricity
Eccentricity is a crucial concept when studying conic sections. It is a measure that describes how much a conic section deviates from being a perfect circle. For any conic section represented by a polar equation, the eccentricity is denoted as \(e\). The value of \(e\) can determine the shape and type of conic section:
- If \(e < 1\), the conic is an ellipse.
- If \(e = 1\), the conic is a parabola.
- If \(e > 1\), the conic is a hyperbola.
Conic Sections
Conic sections arise from slicing a three-dimensional cone with a plane, and each unique slice forms a different conic:
- An ellipse is formed when the plane intersects the cone at an angle, creating an oval shape.
- A parabola occurs when the plane is parallel to the slope of the cone.
- A hyperbola results when the plane slices through both nappes (the two separate pieces) of the cone.
Hyperbola
A hyperbola is one type of conic section characterized by its two divergent branches, giving it a distinct open curve appearance. When the eccentricity \(e\) of a conic section satisfies \(e > 1\), the conic is a hyperbola. This is evident in the exercise, where \(e = 2\). Hyperbolas have intriguing properties:
- They have two branches mirrored across their center.
- Each branch approaches a pair of asymptotes but never touches them.
- The foci of a hyperbola, like in ellipses, are points from which the difference in distances to any point on the hyperbola is constant.
Polar Coordinates
Polar coordinates offer a different perspective from Cartesian coordinates, especially useful when dealing with curves like spirals and conics. In this system, each point is determined by a distance \(r\) from a fixed point, and an angle \(\theta\) from a fixed direction. The polar equation for conics typically takes a form such as \(r = \frac{ed}{1 - e \cos \theta}\) or \(r = \frac{ed}{1 - e \sin \theta}\), depending on the position of the directrix.
- This coordinate system is especially handy for problems involving rotational symmetry.
- It allows for easier integration of angular relationships in equations.
- Transitioning between Cartesian and polar coordinates is often crucial for calculus problems.