Chapter 1: Problem 1
Find the equation of the circle of radius 3 centered at: a) (0,0) b) (5,6) c) (-5,-6) d) (0,3) e) (0,-3) f) (3,0)
Short Answer
Expert verified
(a) \[x^2 + y^2 = 9\], (b) \[(x-5)^2 + (y-6)^2 = 9\], (c) \[(x+5)^2 + (y+6)^2 = 9\], (d) \[x^2 + (y-3)^2 = 9\], (e) \[x^2 + (y+3)^2 = 9\], (f) \[(x-3)^2 + y^2 = 9\].
Step by step solution
01
Understand the Standard Equation of a Circle
The standard equation of a circle is \((x-h)^2 + (y-k)^2 = r^2\), where \((h, k)\) is the center of the circle and \(r\) is the radius. Our task is to find the equation of the circle using this formula with a given center and radius.
02
Applying the Center and Radius Values to the Equation
For each given center, \((h, k)\), use the formula \((x-h)^2 + (y-k)^2 = r^2\) with \(r = 3\). Substitute \(h\) and \(k\) with the given values for each part of the question.
03
Solve for Part a
The center is \((0, 0)\), so the equation is \[(x-0)^2 + (y-0)^2 = 3^2\] which simplifies to \[x^2 + y^2 = 9\].
04
Solve for Part b
The center is \((5, 6)\), so the equation is \[(x-5)^2 + (y-6)^2 = 3^2\] which simplifies to \[(x-5)^2 + (y-6)^2 = 9\].
05
Solve for Part c
The center is \((-5, -6)\), so the equation is \[(x+5)^2 + (y+6)^2 = 3^2\] which simplifies to \[(x+5)^2 + (y+6)^2 = 9\].
06
Solve for Part d
The center is \((0, 3)\), so the equation is \[(x-0)^2 + (y-3)^2 = 3^2\] which simplifies to \[x^2 + (y-3)^2 = 9\].
07
Solve for Part e
The center is \((0, -3)\), so the equation is \[(x-0)^2 + (y+3)^2 = 3^2\] which simplifies to \[x^2 + (y+3)^2 = 9\].
08
Solve for Part f
The center is \((3, 0)\), so the equation is \[(x-3)^2 + (y-0)^2 = 3^2\] which simplifies to \[(x-3)^2 + y^2 = 9\].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Standard Equation of a Circle
A circle in the coordinate plane can be represented by a specific algebraic expression. The **standard equation of a circle** is given by:\[(x-h)^2 + (y-k)^2 = r^2\]where:
Let's illustrate this. Suppose our circle's center is at the origin, (0, 0), and the radius is 3. Plugging these values into the formula:\[(x-0)^2 + (y-0)^2 = 3^2\]This simplifies to:\[x^2 + y^2 = 9\]The resulting equation describes a circle centered at the origin with a radius of 3.
- (h, k) represents the center of the circle.
- r represents the radius of the circle.
Let's illustrate this. Suppose our circle's center is at the origin, (0, 0), and the radius is 3. Plugging these values into the formula:\[(x-0)^2 + (y-0)^2 = 3^2\]This simplifies to:\[x^2 + y^2 = 9\]The resulting equation describes a circle centered at the origin with a radius of 3.
Center of Circle
The **center of a circle** is a crucial element in defining its position on the coordinate plane. It is represented by the coordinates (h, k) in the circle's equation:\[(x-h)^2 + (y-k)^2 = r^2\]
For example, if a center has coordinates (5, 6), the circle's equation becomes:\[(x-5)^2 + (y-6)^2 = r^2\]Here, replacing 3 for the radius:\[(x-5)^2 + (y-6)^2 = 9\]Even with different centers like (-5, -6) or (0, 3), we can swiftly integrate them into the equation without difficulty.
- The x-coordinate of the center is h.
- The y-coordinate of the center is k.
For example, if a center has coordinates (5, 6), the circle's equation becomes:\[(x-5)^2 + (y-6)^2 = r^2\]Here, replacing 3 for the radius:\[(x-5)^2 + (y-6)^2 = 9\]Even with different centers like (-5, -6) or (0, 3), we can swiftly integrate them into the equation without difficulty.
Radius of Circle
The **radius of a circle** is the distance from its center to any point on its circumference. In the standard circle equation:\[(x-h)^2 + (y-k)^2 = r^2\]r is the radius.
A circle's size changes according to this value, but not its shape. Increasing or decreasing the radius stretches or shrinks the circle, respectively.
Consider a circle with radius 3. In this instance, regardless of where the center is located, r remains 3. This means the equation will always look similar in form like so:\[(x-h)^2 + (y-k)^2 = 9\]where 9 is just 3 squared (32). This simplification makes it easy to understand and apply for various circle examples.
A circle's size changes according to this value, but not its shape. Increasing or decreasing the radius stretches or shrinks the circle, respectively.
Consider a circle with radius 3. In this instance, regardless of where the center is located, r remains 3. This means the equation will always look similar in form like so:\[(x-h)^2 + (y-k)^2 = 9\]where 9 is just 3 squared (32). This simplification makes it easy to understand and apply for various circle examples.