MathDB

10. Given a straight line

g

in the plane and a point

O

g

. Construct, without making use of the Parallel Axiom, the half-line perpendicular to

g

at the point

O

and lying in one of the half-planes defined by

g

, under the following restrictions: The construction must be effected by use of a ruler and of a length standard (i.e. an etalon-segment) only; moreover, all lines and points of the construction must lie in the chosen half-plane. (G. 20)

Problem Statement