Proposition.
Drop perpendiculars AA', BB' and CC'
from the vertices of a triangle ABC on any line L. Then the
perpendiculars A'A'', B'B'', and C'C'' to the opposite sides of
the triangle are concurrent at a point P called the orthopole of
triangle ABC and line L.
Click the
red button ()
on the figure to start the animation.
Drag points A, C and line L to change
the figure. Try the step by step
construction.
Dynamic Geometry: You can alter the figure
dynamically in order to test and prove (or disproved)
conjectures and gain mathematical insight that is less
readily available with static drawings by hand.
This page uses the
TracenPoche
dynamic geometry software and requires
Adobe Flash player 7 or higher.
TracenPoche is a project of Sesamath, an association of French
teachers of mathematics.
Instruction to explore the
illustration above:

Animation. Click the red
button
to start/stop animation

Manipulate. Drag points A
and C, and line AC to change the figure.

StepbyStep construction.
Press P and click the left mouse
button
on any free area to show the
stepbystep bar and click 'Next
Step' button ()
to start the construction stepbystep:
Hide the stepbystep bar by
using again the combination P +
click left mouse.
