# Dynamic Geometry 1450: Ortholine, Steiner Line

The orthocenters of the four components triangles (BCE, ABF, ADE, CDF) of a complete quadrilateral ABCDEF lie on a line called Ortholine or Steiner Line.

Complete quadrilateral ABCDEF is the figure determined by four lines, no three of which are concurrent, and their six points of intersection A, B, D, C, E, and F.

### Orthocenter

The orthocenter is the intersection of the three altitudes of a triangle.

## Poster of the Ortholine or Steiner Line using iPad Apps

### Classroom Resource:Interactive step-by-step animation using GeoGebra

This step-by-step interactive illustration was created with GeoGebra.

• To explore (show / hide): click/tap a check box.
• To stop/play the animation: click/tap the icon in the lower left corner.
• To go to first step: click/tap the "Go to step 1" button.
• To manipulate the interactive figure: click/tap and drag the points or figures.

GeoGebra is free and multi-platform dynamic mathematics software for all levels of education that joins geometry, algebra, tables, graphing, statistics and calculus application, intended for teachers and students. Many parts of GeoGebra have been ported to HTML5.