Chapter 8: Problem 44
Graph each circle using a graphing calculator. Use a square viewing window. Give the domain and range. $$(x+2)^{2}+(y+3)^{2}=36$$
Short Answer
Expert verified
The domain is \([-8, 4]\) and the range is \([-9, 3]\).
Step by step solution
01
Identify the Center and Radius of the Circle
The equation of a circle in standard form is \((x-h)^2 + (y-k)^2 = r^2\), where \((h, k)\) is the center and \(r\) is the radius. For the given equation \((x+2)^2 + (y+3)^2 = 36\), we can identify: \(h = -2\), \(k = -3\), and \(r^2 = 36\). Thus, the center is \((-2, -3)\) and the radius \(r = \sqrt{36} = 6\).
02
Graph the Circle
Using a graphing calculator, input the equation \((x+2)^2 + (y+3)^2 = 36\). Select a 'square' viewing window to ensure equal scaling on both axes. A suitable window might be from \(-10\) to \(10\) for both \(x\) and \(y\) axes. This allows the entire circle to be visible with the center at \((-2, -3)\).
03
Determine the Domain of the Circle
The domain of a circle, given its equation and center, is the interval of \(x\)-values it covers. With center at \((-2, -3)\) and radius \(6\), the farthest points on the \(x\)-axis are \(x = -2 - 6 = -8\) and \(x = -2 + 6 = 4\). Thus, the domain is \([-8, 4]\).
04
Determine the Range of the Circle
Similarly, the range is the interval of \(y\)-values covered by the circle. With center at \((-2, -3)\) and radius \(6\), the furthest points on the \(y\)-axis are \(y = -3 - 6 = -9\) and \(y = -3 + 6 = 3\). Thus, the range is \([-9, 3]\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Equation of a Circle
In mathematics, the equation of a circle provides a formula that defines all the points on the perimeter of the circle. The standard form of a circle's equation is given by \[(x - h)^2 + (y - k)^2 = r^2\]where:
- \((h, k)\) represents the coordinates of the circle's center.
- \(r\) represents the radius.
Domain and Range
The domain and range of a circle are essential concepts when graphing and analyzing its position on the Cartesian plane.
- The **domain** refers to the set of possible values for the variable \(x\) that a circle covers. It can be derived from finding how far the circle extends horizontally. For a circle with a center at \((-2, -3)\) and a radius of \(6\), its furthest horizontal reach is \(-8\) (left) to \(4\) (right), thus giving the domain \([-8, 4]\).
- The **range** indicates the possible values for \(y\) the circle covers vertically. Using the same center and radius, the topmost and bottommost points are \(3\) and \(-9\), respectively, resulting in the range \([-9, 3]\).
Graphing Calculator
A graphing calculator is an excellent tool for visualizing mathematical relationships, like those found in circles. You can use it to graph the circle's equation, \((x+2)^2 + (y+3)^2 = 36\), and see how it is positioned on the graph. When inputting this equation into a graphing calculator, remember these simple steps:
- Ensure the calculator is set to graph mode.
- Enter the equation in its standard form.
- Adjust the viewing window to equal dimensions horizontally and vertically. A square window, such as \([-10, 10]\) on both axes, will correctly display the circle without distortion.
Circle Center and Radius
Locating the center and radius of a circle is fundamental in understanding its size and position. When dealing with the standard circle equation, \((x-h)^2 + (y-k)^2 = r^2\), these constants naturally emerge:
- The **center** (\(h, k\)) indicates the point right in the middle of the circle, crucial for any transformations or translations of the circle on the graph.
- The **radius** (\(r\)) gives the fixed distance from the center to any point on the circle. It greatly influences how large or small the circle will appear on the graph.