home construction Thinking
Euclid
Tech
foundation
intermediate
advanced
Euclid's Elements

euclidBook 1: The 48 Propositions
12 To given infinite straight line, from a given point which is not on it, to draw a perpendicular straight line.
Let AB be the given infinite straight line, and C the given point which is not on it. Please enable Java for an interactive construction (with Cinderella).