JIM SMITH JCHS

THE EQUATION OF A CIRCLE ONA GRAPH CAN BE DEFINED AS

( x - h )² + ( y – k )² = r²( h , k ) = center r = radius

IF YOU HAVE THE CENTER AND RADIUS OF A CIRCLE, PLUG IN

TO FIND THE EQUATION.

Center = ( 3 , 6 ) radius = 4 h , k r

( x - h )² + ( y – k )² = r²( x - 3 )² + ( y – 6 )² = 4²( x - 3 )² + ( y – 6 )² = 16

IF YOU HAVE THE CENTER AND RADIUS OF A CIRCLE, PLUG IN

TO FIND THE EQUATION.

Center = ( -5 , 0 ) radius = 8 h , k r

( x - h )² + ( y – k )² = r²( x - -5 )² + ( y – 0 )² = 8²( x + 5 )² + y ² = 64

FIND THE EQUATION OF THE CIRCLE

Center At ( 3 , 9 ) Radius = 5

( x - 3 )² + ( y - 9 )² = 25

(X + 5) ² + ( y - 3 )² = 4

x ² + y ² = 289

Center At ( -5 , 3 ) Radius = 2

Center At ( 0 , 0 ) Radius = 17

IF YOU HAVE THE EQUATION OF A CIRCLE, UNPLUG TO FIND THE

CENTER AND RADIUS.

( x - h )² + ( y – k )² = r² ( h , k ) = center r = radius

( x - 7 )² + ( y – 1 )² = 36Center = 7 , 1Radius = 36 = 6

IF YOU HAVE THE EQUATION OF A CIRCLE, UNPLUG TO FIND THECENTER AND RADIUS.

( x - h )² + ( y – k )² = r² ( h , k ) = center r = radius

( x + 2 )² + ( y + 9 )² = 17( x – (- 2 ) )² + ( y - ( -9 ) )² = 17

Center = -2 , -9Radius = 17

FIND THE CENTER AND RADIUS OF EACH CIRCLE

( x – 11 )² + ( y – 8 )² = 25

( x – 3 )² + ( y + 1 )² = 81

( x + 6 )² + y ² = 21

Center = ( 11,8 ) Radius = 5

Center = ( 3,-1 ) Radius = 9

Center = ( -6,0 ) Radius = 21

YOU NEED TO KNOW THE CENTER AND RADIUSTO FIND THE EQUATION OF A CIRCLE.

If A Circle Has A Center At ( 2 , 4)And Passes Through (4 , 8 ),

What Is The Equation Of The Circle?

Center At ( 2 , 4) Passes Through (4 , 8 )

( x - 2 )² + ( y - 4 )² = r²

The Radius Is The Distance From The Center To A Point On The Circle.

r = (x-x)² + (y-y)² r = ( 4 – 2 )² + ( 8 – 4 )²r = 2² + 4² = 20

( x - 2 )² + ( y - 4 )² = 20 ²

( x - 2 )² + ( y - 4 )² = 20

FIND THE EQUATION OF THE CIRCLE

Center At ( 3 , 6 ) Passes Through ( 1 , 5 )

Center At ( 0 , 5 ) Passes Through ( 6 , 2 )

Center At ( -3 , 1 ) Passes Through (-4 , -4 )

( x - 3 )² + ( y - 6 )² = 5

x ² + ( y - 5 )² = 45

( x + 3 )² + ( y – 1 )² = 26