Menelaus Theorem (Introduction)
- Author:
- GeoGebra Materials Team
Transversal of a Triangle
The black line JK is a transversal of triangle ABC. It intersects the sides of the triangle. An intersection can take place on the extended sides, which are the dotted lines.
Drag the objects in the diagram and see if you agree with the following statements.
Note: we assume line JK does not contain a side or vertex of triangle ABC.
1. If JK is parallel to one of the sides, then it intersects the other two sides in two points. Those two points are both either inside or outside the triangle
2. If JK is not parallel to any side, then it intersects all three sides. In this case, see if you agree: line JK intersects the triangle in exactly one or three of the extended sides.