Chapter 11: Problem 28
Make the required change in the given equation. \(r=2 \sin \theta\) to Cartesian coordinates
Short Answer
Expert verified
The Cartesian equation is \( y = 2 \).
Step by step solution
01
Identify Polar Equations
The given equation is in polar coordinates: \( r = 2 \sin \theta \). In polar coordinates, \( r \) represents the radius from the origin, and \( \theta \) is the angle from the positive x-axis. Our goal is to transform this equation into Cartesian coordinates, where equations have variables \( x \) and \( y \).
02
Apply Polar to Cartesian Conversion Formulas
In Cartesian coordinates, we can relate \( x \) and \( y \) to \( r \) and \( \theta \) using these formulas:- \( x = r \cos \theta \)- \( y = r \sin \theta \)- \( r = \sqrt{x^2 + y^2} \)We will primarily use \( y = r \sin \theta \) to help with our conversion.
03
Express \( r \sin \theta \) in Terms of \( y \)
From the formula \( y = r \sin \theta \), we can substitute \( r \sin \theta \) with \( y \). Thus, we can write the equation \( r = 2 \sin \theta \) as:\[ r \sin \theta = y \ \Rightarrow y = 2 \]
04
Understand the Cartesian Equation
The equation \( y = 2 \) is a Cartesian equation that represents a horizontal line two units above the x-axis in the Cartesian plane. This is the conversion of the original polar equation into Cartesian coordinates.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Polar Coordinates
Polar coordinates system is a method of mapping out points on a plane using a circle-based approach. Instead of using x and y like the Cartesian system, polar coordinates describe a point's position relative to a central point (the origin) using two values:
- Radius \( r \): This is the distance from the origin to the point.
- Angle \( \theta \): This measures the angle from the positive x-axis to the point, counterclockwise.
Cartesian Coordinates
The Cartesian coordinate system, named after René Descartes, is used to specify each point uniquely on a plane using ordered pairs. It is one of the most commonly used coordinate systems in mathematics and has two main components:
- \( x \): The horizontal position, typically measured along a straight line from the origin.
- \( y \): The vertical position, measured perpendicular to the x-axis.
Conversion Formulas
To bridge the gap between polar and Cartesian coordinates, conversion formulas are essential. These formulas allow us to express a point defined in one system into the other one.
- \( x = r \cos \theta \): Converts the radius and angle into the horizontal Cartesian coordinate.
- \( y = r \sin \theta \): Transforms polar coordinates to the vertical Cartesian coordinate.
- \( r = \sqrt{x^2 + y^2} \): Used to find the radius from Cartesian coordinates.
- \( \theta = \tan^{-1}(\frac{y}{x}) \): Assists in finding the angle from the x-axis.
Horizontal Line in Cartesian Plane
In the Cartesian coordinate system, a horizontal line holds a special position. It is characterized by having the same y-coordinate for all points on the line, which means it runs parallel to the x-axis.
- The equation \( y = c \) describes a horizontal line, where \( c \) is a constant value.
- For example, \( y = 2 \) indicates a line that crosses the y-axis at 2 and extends in both horizontal directions.