Complex sentence: The problem of constructing an angle of a given measure is equivalent to constructing two segments such that the ratio of their length is because one may pass from one solution to the other by a compass and straightedge construction.
Split into simpler sentences: The problem of constructing an angle of a given measure is equivalent to constructing two segments such that the ratio of their length is. From a solution to one of these two problems, one may pass to a solution of the other by a compass and straightedge construction.