Definition of a circle

1. DEFINITION OF A CIRCLE
Let C be a given point. The set of all points P having the same distance from C is called a circle.
The point C is called the center of the circle, and the common distance its radius.
Mathematical Key Points
(1) The standard equation formula of a circle is:
(2) The coordinate for the center is:
(3) The radius would be:
EXAMPLES:
(1) What is the standard equation of a circle if the center is (3, 1) and the radius is 5?
SOLUTION:
(2) What is the standard equation of a circle of the center is (- 5, - 6) and the radius is 6?
SOLUTION:

2. (3) What is the center and radius of the equation
SOLUTION:
(h) (k)
Center =
Radius = ( ) (√ √ )