Writing Equations of Circles from Graphs

Drag point A. Drag point B.
What is the equation of the circle?
To write the equation, you need to know the coordinates of the center and the radius!
When you think you know the equation, type the equation into the INPUT line. 
You must use "SQRT( )" for the square root and "^" for the exponent.

REMEMBER! You must graph the "top half" and "bottom half" separately!

Example: To graph the circle  (x+5)2+(y+3)2=16

  1. You first graph the TOP HALF of the circle:  
Enter the equation sqrt(16-(x+5)^2) -3 in the INPUT line. Press ENTER.
  1. Then you graph the BOTTOM HALF of the circle: 
Enter the equation  -1*sqrt(16-(x+5)^2) -3  in the INPUT line. Press ENTER.


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Steve Phelps, Created with GeoGebra