TOOL (.ggt): [url]http://www.geogebratube.org/material/show/id/87369[/url]
[b]Altitude[A,B,C, m][/b]
[math]\;\;[/math] A,B,C three points in space,
[math]\;\;[/math] m a margin for the base line
gives
-the altitude from C onto AB,
-the base point of the altitude, C'
-the (right) angle ∡CC'A
-base segment ABC' containing all three points
