Chapter 10: Problem 48
Find the center and the radius of each circle. Then graph the circle. $$(x-2)^{2}+(y+3)^{2}=100$$
Short Answer
Expert verified
Center: (2, -3), Radius: 10
Step by step solution
01
Identify the Standard Form of the Circle
The equation \((x-2)^2 + (y+3)^2 = 100\) is in the standard form of a circle, which is \((x-h)^2 + (y-k)^2 = r^2\).
02
Determine the Center
In the standard form \((x-h)^2 + (y-k)^2 = r^2\), \(h\) and \(k\) represent the coordinates of the center of the circle. Here, \h = 2\ and \k = -3\. So, the center of the circle is \((2, -3)\).
03
Find the Radius
The constant on the right side of the standard form equation represents \r^2\. In this equation, \(r^2 = 100\). To find the radius, take the square root of 100: \r = \sqrt{100} = 10\. Thus, the radius of the circle is 10 units.
04
Graph the Circle
To graph the circle, plot the center at \(2, -3)\). From the center, measure and mark points 10 units away in all directions (up, down, left, and right). These marks will help to sketch the circle accurately.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Standard Form of a Circle
Understanding the standard form of a circle is crucial. The standard form of a circle equation is expressed as \((x-h)^2 + (y-k)^2 = r^2\). Here:
Let’s parse an example: For the equation \((x-2)^2 + (y+3)^2 = 100\), it aligns perfectly with the standard form.
- \(h\) and \(k\) are the x and y coordinates of the circle's center.
- \(r\) is the radius of the circle.
Let’s parse an example: For the equation \((x-2)^2 + (y+3)^2 = 100\), it aligns perfectly with the standard form.
Center of a Circle
The center of a circle in the standard form equation \((x-h)^2 + (y-k)^2 = r^2\) can be easily identified. The terms \(h\) and \(k\) represent the x and y coordinates of the center. Therefore, if our equation is \((x-2)^2 + (y+3)^2 = 100\),
We observe:
It helps to remember this simple rule:
We observe:
- \(h = 2\)
- \(k = -3\)
It helps to remember this simple rule:
- Subtracting a number inside the parenthesis means the center moves to the positive direction of that axis.
- Adding a number means it moves to the negative direction of that axis.
Radius of a Circle
In the standard form equation \((x-h)^2 + (y-k)^2 = r^2\), \(r\) stands for the radius of the circle. To determine the radius, take the square root of the constant on the right-hand side.
Let's break it down with our example:
Let's break it down with our example:
- Equation: \((x-2)^2 + (y+3)^2 = 100\)
- Here, \(r^2 = 100\)
- To find \(r\), we take the square root of 100
- Thus, \(r = \sqrt{100} = 10\)
Graphing Circles
To graph a circle given its standard form equation, follow these steps:
Join these points smoothly to visualize the circle. This care in plotting ensures the circle is accurately represented on the graph.
- Plot the center located at \(h, k\).
- From the center, measure the radius distance in all four main directions: up, down, left, and right.
- Mark these points.
- Connect these points in a smooth, round shape to complete the circle.
- Center at \(2, -3\)
- Radius of 10 units
Join these points smoothly to visualize the circle. This care in plotting ensures the circle is accurately represented on the graph.