Chapter 5: Problem 4
Write an equation of the circle centered at (-9,9) with radius 16 .
Short Answer
Expert verified
The equation of the circle is \((x + 9)^2 + (y - 9)^2 = 256\).
Step by step solution
01
Identify the Standard Equation of a Circle
The standard equation of a circle in the Cartesian coordinate system is given by \((x - h)^2 + (y - k)^2 = r^2\), where \((h, k)\) is the center of the circle and \(r\) is its radius.
02
Substitute the Center Coordinates
Identify the circle's center coordinates \((-9, 9)\), then substitute them into the formula. This gives \((x + 9)^2 + (y - 9)^2 = r^2\).
03
Substitute the Radius
The radius of the circle is 16. Substitute \(r = 16\) into the equation. This results in \((x + 9)^2 + (y - 9)^2 = 16^2\).
04
Simplify the Equation
Calculate \(16^2\) to simplify the equation: \(16^2 = 256\). This gives the final equation \((x + 9)^2 + (y - 9)^2 = 256\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Cartesian Coordinate System
The Cartesian coordinate system is a method of representing geometric figures through a series of numerical coordinates along two perpendicular axes.
These axes are typically labeled as the x-axis and the y-axis. Each point in this system is identified by a pair of numbers, \(x, y\).
This makes it easy to plot shapes and lines in a two-dimensional space, allowing for visual representation and analysis:
These axes are typically labeled as the x-axis and the y-axis. Each point in this system is identified by a pair of numbers, \(x, y\).
This makes it easy to plot shapes and lines in a two-dimensional space, allowing for visual representation and analysis:
- The x-axis is the horizontal line where \(x\) values lie.
- The y-axis is the vertical line where \(y\) values reside.
- The origin, denoted as \(0,0\), is the point where these two axes intersect.
Standard Form of a Circle
A circle in the Cartesian coordinate system is best understood using its standard form equation: \((x-h)^2+(y-k)^2=r^2\).
This formula is crucial as it allows us to clearly define the circle's position and measure its size. Here’s what each component signifies:
This formula is crucial as it allows us to clearly define the circle's position and measure its size. Here’s what each component signifies:
- \(h\) and \(k\) are the x and y coordinates of the circle's center, respectively.
- \(r\) represents the radius of the circle.
- If you know the center of a circle is at (-9, 9) and the radius is 16, you can immediately plug these into the standard form.
- This yields \((x + 9)^2 + (y - 9)^2 = 256\).
Radius of a Circle
The radius of a circle is a key characteristic that defines its extent. It is the distance from the center of the circle to any point on its perimeter.
In the equation of a circle, the radius is represented by \(r\).
In the equation of a circle, the radius is represented by \(r\).
- The radius is always a positive number and significantly contributes to the size of the circle.
- In the aforementioned equation \((x-h)^2 + (y-k)^2 = r^2\), the radius is squared, turning the equation into \(r^2\) form.
- Calculate the square of the radius, getting \(16^2 = 256\).
- Incorporate this result into the circle's equation: \((x + 9)^2 + (y - 9)^2 = 256\).