From GeoGebra Manual
- AreConcurrent[ <Line>, <Line>, <Line> ]
- Decides if the lines are concurrent. If the lines are parallel, they considered to have a common point in infinity, thus this command returns true in this case.
Normally this command computes the result numerically. This behavior can be changed by using the Prove command.
AreConcurrent[Line[(1, 2), (3, 4)], Line[(1, 2), (3, 5)], Line[(1, 2), (3, 6)]]yields true since all three lines contain the point (1,2).