Did you know that we can draw perpendicular lines using just a straightedge and a compass (without a set square)? In that case, we say that we CONSTRUCT perpendicular lines.
To learn how to do it, watch this video.
1st part of the video:
For given line a and point T on this line, we construct line b which is perpendicular to the line a and goes through point T.
For given line c and external point T, we construct line d which goes through point T and is perpendicular to line c.
Constructing perpendicular lines on paper.
Video without words.
Thanks to Rex Boggs, Rockhampton Grammar School, Australia (http://bit.ly/rexboggs ) for help with the English translation.
Music by longzijun, http://longzijun.wordpress.com/ .
My math materials in English: http://www.antonija-horvatek.from.hr/~ahorvate/materials-English.htm .
My (whole) website: http://www.antonija-horvatek.from.hr/ .