# Investigating the Equation of a Circle

- Author:
- Chi Tran, kortiz, GeoGebra Team German

- Topic:
- Circle

Drag the center of the circle and the radius of the circle to answer the questions below.

1) Drag point B to change the radius to 2, 3, 6, 10. How does this change the equation of the circle?
2) Using a radius of 3, drag point A to change the center of the circle to (5, 3) , then change it to (-5, 3). How does this change the equation of the circle?
3) Using a radius of 3, drag point A to change the center of the circle to (2, 6) , then change it to (2, -6). How does this change the equation of the circle?
4) Using a radius of 3, drag point A to change the center of the circle to (4, 0), then change it to (0, 4). How does this change the equation of the circle?
5)Write the equation of a circle with a center of (-2, 1) and a radius of 7. Check your answer by graphing the circle.
6) Write the equation of a circle with a center (0, 0) and a radius of 9. Check your answer by graphing.
7) Write the equation of a circle with a center (h, k) and a radius of r .