Chapter 10: Problem 15
Identify the curve by finding a Cartesian equation for the curve. \(r^{2}=5\)
Short Answer
Expert verified
The curve is a circle centered at the origin with radius \( \\sqrt{5} \).
Step by step solution
01
Understand the Equation
The equation given is \( r^{2} = 5 \), where \( r \) is the radial coordinate in polar coordinates. This represents all points at a fixed distance from the origin.
02
Recall Cartesian to Polar Conversion
In polar coordinates, the relationship between \( r \) and Cartesian coordinates \( (x, y) \) is given by \( r = \sqrt{x^2 + y^2} \). This is crucial for converting the given polar equation to Cartesian form.
03
Substitute the Polar Equation
Substitute \( r = \sqrt{x^2 + y^2} \) into the given polar equation \( r^2 = 5 \). This yields \( (\sqrt{x^2 + y^2})^2 = 5 \).
04
Simplify the Equation
Once substituted, simplify the equation. The equation \( (\sqrt{x^2 + y^2})^2 = 5 \) becomes \( x^2 + y^2 = 5 \).
05
Identify the Cartesian Equation Type
The resultant equation \( x^2 + y^2 = 5 \) is recognized as the equation of a circle in Cartesian coordinates, with the circle centered at the origin (0, 0) and with a radius \( \sqrt{5} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Polar Coordinates
Polar coordinates provide a way of describing points in a plane using angles and distances. Instead of horizontal and vertical distances like Cartesian coordinates, polar coordinates use:
- A radial coordinate, \( r \), which measures how far the point is from the origin.
- An angular coordinate, \( \theta \), which measures the angle made with the positive x-axis.
Cartesian Coordinates
The Cartesian coordinate system is perhaps the most familiar method of plotting points on a plane. It uses two perpendicular axes: the horizontal x-axis and the vertical y-axis.
- Every point on the plane is defined by a pair of numbers \((x, y)\), where \(x\) is the horizontal position and \(y\) is the vertical position.
- The system is excellent for describing straight lines, parabolas, and other algebraic curves directly.
- x = r \cos(\theta)
- y = r \sin(\theta)
Equation of a Circle
The equation of a circle in the Cartesian coordinate system is typically expressed as \( (x - h)^2 + (y - k)^2 = r^2 \). Here, \((h, k)\) represents the circle's center, and \(r\) is the radius. When a circle is centered at the origin, the equation simplifies to \(x^2 + y^2 = r^2\), which is our case where \(x^2 + y^2 = 5\).
This standard form helps easily visualize and understand the circle's size and position on the plane:
This standard form helps easily visualize and understand the circle's size and position on the plane:
- The center is at the origin \((0,0)\).
- The radius is \( \sqrt{5} \) since we have \(r^2 = 5\), indicating the circle stretches out evenly from the center by that distance.