Graphs of Circles Worksheets
How to Find the Equation of a Circle Based on the Diameter and the Center Point  A circle is a set of all points in a plane at a defined distance known as the radius and for the given point called the center. Apart from the radius and center, a circle includes various parts in its geometry. A line segment connecting the two points on the circle and passes through the center of the circle is known as the diameter of the circle. Let's assume that point (x, y) are the coordinates given on the circle. The center of the circle will be at (h, k), and the radius will be defined as the 'r'. Using the distance formula to find the equation of the circle. √(x_{2}  x_{1})^{2} + (y_{2} – y_{1})^{2} = d Substituting (x1 , y1) = (h, k) and (x2 , y2) = (x, y) and d = r √( x – h)^{2} + (y – k)^{2} = r Squaring each side (x – h)^{2} + (y – k )^{2}= r^{2} The equation of the circle with radius r units and the center (h, k) is (x – h)^{2} + (y – k )^{2} = r^{2}.

Basic Lesson
Demonstrates how to determine the equation of a circle. Practice problems are provided. Write the equation of a circle that has a center at (1, 2) and a radius of 2?
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Intermediate Lesson
Explores how to find the coordinates of the center of a circle based on the equation of the circle. Practice problems are provided. What are the coordinates of the center of this circle? (x  2)^{2} + (y  3)^{2} = 9.
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Independent Practice 1
Example: Write the equation of a circle that has a center at (2, 3) and radius of 8? The answers can be found below.
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Homework Worksheet
12 Graphs of Circles problems for students to work on at home. Example problems are provided and explained.
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The Lottery
A mathematician organizes a lottery in which the prize is an infinite amount of money. When the winning ticket is drawn, and the jubilant winner comes to claim his prize, the mathematician explains the mode of payment: "1 dollar now, 1/2 dollar next week, 1/3 dollar the week after that...