CIRCLES

1
CIRCLES

• Topic 7.3

2
Definitions

• Circle The set of all points that are the same
  distance from the center
• Radius a segment whose endpoints are the center
  and a point on the circle

3
Equation of a Circle
4
Writing the Equation of a Circle

• Group x terms together, y-terms together, and
  move constants to the other side
• Complete the square for the x-terms
• Remember that whatever you do to one side, you
  must also do to the other
• Complete the square for the y-terms
• Remember that whatever you do to one side, you
  must also do to the other

5
Example Write the equation and find the center
and radius length of
Group terms
Complete the square
6
You try!! Write the equation and find the center
and radius length of
7
THINK ABOUT IT
Find the center, the length of the radius, and
write the equation of the circle if the endpoints
of a diameter are (-8,2) and (2,0).
Center Use midpoint formula!
Length use distance formula with radius and an
endpoint
Equation Put it all together