From GeoGebra Manual
- Circle[ <Point M>, <Number r> ]
- Yields a circle with center M and radius r.
- Circle[ <Point M>, <Segment> ]
- Yields a circle with center M and radius equal to the length of the given segment.
- Circle[ <Point M>, <Point A> ]
- Yields a circle with center M through point A.
- Circle[ <Point A>, <Point B>, <Point C> ]
- Yields a circle through the given points A, B and C.
- Note: See also Compass, Circle with Center through Point, Circle with Center and Radius, and Circle through Three Points tools.
| Following text is about a feature that is supported only in GeoGebra 5.0.
Note: From GeoGebra 5, this command will work in 3D with 3D Points as well
Use circles to fix the distance between two objects
Circles are a great way to make the distance between two objects constant: If there are two points A and B on two lines g (point A) and h (point B) where A can be moved and B should have the constant distance r to A you can define B as the intersection between the line h and the circle around A with the radius r. As a circle intersects a line at two points (in case it's not tangetial or passing by) you have to hide & ignore the second intersection.